Optical system and imaging device

ABSTRACT

An optical apparatus has a look-up table provided with control information for controlling an optimum variable optical-property optical element in accordance with a distance to an object, a zoom state, or a combination of the distance to the object with the zoom state. A drive of the variable optical-property optical element is controlled on the control information obtained from the look-up table or a predetermined calculation process is executed on the control information obtained from the look-up table, and information obtained from the calculation process is used to control the drive of the variable optical-property optical element.

This is a divisional of U.S. application Ser. No. 10/242,350, filed Sep.13, 2002, now U.S. Pat. No. 6,747,813 the contents of which areincorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a variable optical-property optical elementsuch as a variable focal-length lens, a variable focal-lengthdiffraction optical element, a variable deflection-angle prism, or adeformable mirror, and to an optical apparatus such as spectacles, avideo projector, a digital camera, a TV camera, an endoscope, atelescope, or a camera finder, having an optical system including such avariable optical-property optical element.

2. Description of Related Art

Conventional lenses have been manufactured by polishing glass. Since thelens itself cannot vary a focal length, a mechanical structure iscomplicated because a lens unit must be moved along the optical axis forfocusing or zooming of a camera, or changing magnification.

Because a motor or the like is used for moving a part of the lens unit,this conventional practice has disadvantages that power consumption islarge, noise is produced, response time is long, and much time isrequired for moving lenses.

For shake prevention as well, mechanical movement of the lenses by amotor or a solenoid causes defects such as a large power consumption anda complicate mechanical structure, resulting in a higher cost.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide avariable optical-property optical element such as a variablefocal-length lens, a deformable mirror, or a variable deflection-angleprism, which is low in power consumption, quiet, short in response time,and simple in mechanical structure and contributes to cost reduction,and an optical system and an imaging device or an optical apparatus,including such variable optical-property optical elements.

In order to achieve this object, the optical system, for example,according to the present invention is provided with a deformable mirror,which bends the optical axis to form an image of an object on an imagingplane. In this case, the optical system has a two-dimensional look-uptable (LUT), with a zoom state and a distance to an object as inputinformation, storing the value of a voltage applied or a currentsupplied to the deformable mirror, as output information, whichcorresponds to the zoom state and the distance to the object. Thetwo-dimensional LUT is scanned in turn in image formation and the valueof the voltage applied or the current supplied to the deformable mirroris changed in accordance with acquired output information to determinethe sharpness of a formed image so that the output information of thetwo-dimensional LUT where the sharpness of the formed imaged isoptimized is decided as the value of the voltage applied or the currentsupplied to the deformable mirror.

The optical system, for example, according to the present invention issuch that when one of the zoom state and the distance to the object isdetectable in image formation, the zoom state or the distance to theobject, having been detected, is fixed. The two-dimensional LUT isscanned in turn in image formation and the value of the voltage appliedor the current supplied to the deformable mirror is changed inaccordance with acquired output information to determine the sharpnessof a formed image so that the output information of the two-dimensionalLUT where the sharpness of the formed imaged is optimized is decided asthe value of the voltage applied or the current supplied to thedeformable mirror.

The optical system, for example, according to the present invention isprovided with a deformable mirror, which bends the optical axis to forman image of an object on an imaging plane. In this case, the opticalsystem has a two-dimensional look-up table (LUT), with a zoom state anda distance to an object as input information, storing the value of avoltage applied or a current supplied to the deformable mirror, asoutput information, which corresponds to the zoom state and the distanceto the object. When one of the zoom state and the distance to the objectis detectable in image formation, the zoom state and the distance to theobject are fixed to input the two-dimensional LUT so that acquiredoutput information is decided as the value of the voltage applied or thecurrent supplied to the deformable mirror.

The imaging device, for example, according to the present invention ismounted with a zoom lens. In this case. the imaging device has avariable mirror.

Further, the imaging device, for example, according to the presentinvention has at least two variable mirrors.

Still further, the imaging device, for example, according to the presentinvention uses the variable mirror as a focusing means.

This and other objects as well as the features and advantages of thepresent invention will become apparent from the following detaileddescription of the preferred embodiments when taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing schematically an example of a fundamentalarrangement of an optical system in the present invention;

FIG. 2 is a view showing an example of the structure of a deformablemirror used in the optical system of FIG. 1;

FIGS. 3A and 3B are plan views showing the structures of a frame memberand a lower substrate, respectively, in accordance with individualsubstrates of the deformable mirror of FIG. 2;

FIGS. 4A and 4B are views showing another example of the deformablemirror used in the optical system of FIG. 1;

FIGS. 5A and 5B are views showing still another example of thedeformable mirror used in the optical system of FIG. 1;

FIG. 6 is a diagram showing an example of the evaluation of sharpness,used in the optical system of the present invention;

FIG. 7 is a block diagram for determining a voltage applied to thedeformable mirror in the optical system of a first embodiment of thepresent invention;

FIG. 8 is a graph showing approximate curves relative to the appliedvoltage versus the distance to the object that is one example wherediscrete data used in the optical system of the present invention areconverted into approximate curves;

FIG. 9 is a block diagram for determining a voltage applied to thedeformable mirror in the optical system of a second embodiment of thepresent invention;

FIG. 10 is a block diagram for determining a voltage applied to thedeformable mirror in the optical system of a third embodiment of thepresent invention;

FIG. 11 is a block diagram for determining a voltage applied to thedeformable mirror in the optical system of a fourth embodiment of thepresent invention;

FIG. 12 is a block diagram showing one example where the voltage isapplied to the deformable mirror in the optical system in which anoptical element of the present invention is not zoom-driven;

FIG. 13 is a block diagram showing another example where the voltage isapplied to the deformable mirror in the optical system in which anoptical element of the present invention is not zoom-driven;

FIG. 14 is a view showing schematically the imaging device of a fifthembodiment of the present invention;

FIGS. 15A and 15B are perspective and sectional views, respectively,showing the shape of the deformable mirror used in the presentinvention;

FIGS. 16A and 16B are sectional views showing schematicallyarrangements, developed along the optical axis, at wide-angle andtelephoto positions, respectively, of the optical system of the fifthembodiment;

FIG. 17 is a flowchart showing a control process in the imaging deviceof the fifth embodiment;

FIG. 18 is a view showing schematically the imaging device of a sixthembodiment of the present invention;

FIG. 19 is a block diagram showing the process of a contrast AF systemin a CPU;

FIG. 20 is a graph showing a focus signal derived from the process ofthe contrast AF system of FIG. 19 versus the focus position of theoptical system of the imaging device of a seventh embodiment accordingto the present invention;

FIG. 21 is a flowchart showing the control process in the imaging deviceof the seventh embodiment;

FIG. 22 is a view showing schematically the imaging device of an eighthembodiment of the present invention;

FIG. 23 is a flowchart showing the control process in the imaging deviceof the eighth embodiment;

FIG. 24 is a flowchart showing the control process in the imaging deviceof a ninth embodiment according to the present invention;

FIG. 25 is a view showing schematically the imaging device of a tenthembodiment of the present invention;

FIGS. 26A and 26B are sectional views showing schematicallyarrangements, developed along the optical axis, at wide-angle andtelephoto positions, respectively, of the optical system of the tenthembodiment;

FIG. 27 is a view showing schematically the imaging device of aneleventh embodiment of the present invention;

FIG. 28 is a view showing schematically the imaging device of athirteenth embodiment of the present invention;

FIG. 29 is a view showing schematically the imaging device of afourteenth embodiment of the present invention, using a variablefocal-length lens;

FIGS. 30 and 31 are views showing other examples of the imaging deviceof the fourteenth embodiment, using variable focal-length lenses;

FIG. 32 is a view showing schematically a Keplerian finder for a digitalcamera using a variable optical-property mirror as the deformable mirrorused in the imaging device of the present invention;

FIG. 33 is a view showing schematically another embodiment of thedeformable mirror used as a variable mirror according to the presentinvention;

FIG. 34 is an explanatory view showing one aspect of electrodes used inthe deformable mirror of the embodiment of FIG. 33;

FIG. 35 is an explanatory view showing another aspect of electrodes usedin the deformable mirror of the embodiment of FIG. 33;

FIG. 36 is a view showing schematically another embodiment of thedeformable mirror used as the variable mirror of the present invention;

FIG. 37 is a view showing schematically another embodiment of thedeformable mirror used as the variable mirror of the present invention;

FIG. 38 is a view showing schematically another embodiment of thedeformable mirror used as the variable mirror of the present invention;

FIG. 39 is an explanatory view showing the winding density of athin-film coil in the embodiment of FIG. 38;

FIG. 40 is a view showing schematically another embodiment of thedeformable mirror used as the variable mirror of the present invention;

FIG. 41 is an explanatory view showing an example of an array of coilsin the embodiment of FIG. 40;

FIG. 42 is an explanatory view showing another example of the array ofcoils in the embodiment of FIG. 40;

FIG. 43 is an explanatory view showing an array of permanent magnetssuitable for the array of coils of FIG. 42 in the embodiment of FIG. 38;

FIG. 44 is a view showing schematically an imaging system using thedeformable mirror as the variable mirror applicable to an opticalapparatus in another embodiment of the present invention;

FIG. 45 is a view showing schematically the deformable mirror in anotherembodiment of the deformable mirror of the present invention;

FIG. 46 is a view showing schematically an example of a micropumpapplicable to the variable mirror used in the imaging device of thepresent invention;

FIG. 47 is a view showing the principle of a variable focal-length lensused in the imaging device of the present invention;

FIG. 48 is a view showing the index ellipsoid of a nematic liquidcrystal molecule of uniaxial anisotropy;

FIG. 49 is a view showing a state where an electric field is applied tothe macromolecular dispersed liquid crystal layer of the variablefocal-length lens in FIG. 47;

FIG. 50 is a view showing one example where a voltage applied to themacromolecular dispersed liquid crystal layer in FIG. 47 can be changed;

FIG. 51 is a view showing the construction of an imaging optical systemfor digital cameras which uses the variable focal-length lens of FIG.50;

FIG. 52 is a view showing one example of a variable focal-lengthdiffraction optical element applicable to the imaging device of thepresent invention;

FIG. 53 is a view showing variable focal-length spectacles, each havinga variable focal-length lens which uses a twisted nematic liquidcrystal;

FIG. 54 is a view showing the orientation of liquid crystal moleculeswhere a voltage applied to a twisted nematic liquid crystal layer ofFIG. 53 is increased:

FIGS. 55A and 55B are views showing two examples of variabledeflection-angle prisms, each of which is applicable to the imagingdevice of the present invention;

FIG. 56 is a view for explaining the applications of the variabledeflection-angle prisms shown in FIGS. 55A and 55B;

FIG. 57 is a view showing a variable focal-length mirror applying thevariable focal-length lens used in the imaging device of the presentinvention;

FIG. 58 is a view showing schematically an imaging unit using thevariable focal-length lens in another embodiment of the variablefocal-length lens used in the imaging device of the present invention;

FIG. 59 is an explanatory view showing a modified example of thevariable focal-length lens in the embodiment of FIG. 58;

FIG. 60 is an explanatory view showing a state where the variablefocal-length lens of FIG. 59 is deformed;

FIG. 61 is a view showing schematically another embodiment of thevariable focal-length lens used in the imaging device of the presentinvention;

FIG. 62 is a view showing schematically the variable focal-length lensusing a piezoelectric substance in another embodiment of the variableoptical-property optical element applicable to the imaging device of thepresent invention;

FIG. 63 is an explanatory view showing a state where the variablefocal-length lens of FIG. 62 is deformed;

FIG. 64 is a view showing schematically the variable focal-length lensusing two thin plates made with piezoelectric substances in stillanother embodiment of the variable optical-property optical elementapplicable to the imaging device of the present invention;

FIG. 65 is a view showing schematically still another embodiment of thevariable focal-length lens used in the imaging device of the presentinvention;

FIG. 66 is an explanatory view showing a state of the deformation of thevariable focal-length lens in FIG. 65;

FIG. 67 is a view showing schematically the variable focal-length lensusing a photomechanical effect in a further embodiment of the variableoptical-property optical element applicable to the imaging device of thepresent invention;

FIGS. 68A and 68B are explanatory views showing the structures ofazobenzene of trans- and cis-type, respectively, used in the variablefocal-length lens of FIG. 67; and

FIG. 69 is a view showing schematically still another embodiment of thedeformable mirror used as the variable mirror in the imaging device ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the drawings, the embodiments of the presentinvention will be described below. FIG. 1 shows an example of afundamental arrangement of an optical system in the present invention.The optical system of the present invention has an optical element 1 anda deformable mirror 2 and is constructed so that the optical axis oflight from an object is bent by the deformable mirror 2 and an image isformed on an image sensor 3. In the optical element 1, a lens unit 1 ais arranged so that a predetermined lens constituting the lens unit 1 acan be moved along the optical axis. The lens unit 1 a has a variatorfunction for changing the magnification of the optical system. In FIG.1, the deformable mirror 2 is conveniently shown by only its reflectingsurface.

In this optical system, the settings of zoom states at wide-angle,standard and telephoto positions and a focus adjustment are made by themovement of the predetermined lens constituting the lens unit 1 a and achange of the profile (a change in curvature) of the reflecting surfaceof the deformable mirror 2. When the change of the profile of thereflecting surface of the deformable mirror 2 is slight, it isrecommended that the zoom state is determined by the movement of thepredetermined lens constituting the lens unit 1 a and the focusadjustment is made by the change of the profile of the reflectingsurface of the deformable mirror 2. Also, moving lenses may beconstructed with a plurality of lens units.

FIG. 2 shows an example of the structure of the deformable mirror 2 usedin the optical system of FIG. 1. FIG. 3A shows the structure of a framemember of the deformable mirror in FIG. 1, and FIG. 3B shows thestructure of a lower substrate thereof. In FIG. 3A, the reflectingsurface is indicated by a solid line and a conductive portion by abroken line.

The deformable mirror 2 includes a reflecting surface and conductiveportion 2 a and a flexible thin film 2 b in a frame member 2 e, and anelectrode 2 c for deforming the reflecting surface, provided opposite tothe flexible thin film 2 b in a lower substrate 2 f. In the deformablemirror shown in FIG. 2 and FIGS. 3A and 3B, the reflecting surface iscombined with the conductive portion by using a metallic thin film withhigh reflectance such as aluminum. Between the conductive portion 2 aand the electrode 2 c, a voltage is applied, or a current is supplied,from external lead electrodes 2 d, and thereby the reflecting surface isdeformed by an electrostatic force exerted between them so that itscurvature is changed. Also, in FIG. 2 and FIGS. 3A and 3B, theconnection of the conductive portion 2 a and the electrode 2 c with theexternal lead electrodes 2 d is omitted.

The deformable mirror 2 may be constructed as shown in FIGS. 4A and 4Band FIGS. 5A and 5B. In the deformable mirror of FIGS. 4A and 4B, eachof the electrode 2 c for deformation and the external lead electrode 2 dprovided on the lower substrate 2 f is divided into a plurality ofsegments so that different voltages can be applied, or differentcurrents can be supplied, to individual electrodes. Whereby, it becomespossible to impart the distribution with the place to the electrostaticforce exerted between the reflecting surface and the electrode 2 cdivided into the plurality of segments, and a deformed profile of thereflecting surface can be optimized more strictly.

In the deformable mirror shown in FIGS. 5A and 5B, the conductiveportion is divided and its effect is the same as that shown in FIGS. 4Aand 4B.

In the optical system shown in FIG. 1, the profile of the reflectingsurface of the deformable mirror 2 most suitable for the focusadjustment and correction for aberration varies according to the zoomstate and a distance from the surface of a first lens 1 ₁ to the object.It is thus necessary to optimize the voltage applied or the currentsupplied to the deformable mirror 2 in accordance with the zoom stateand the distance from the surface of the first lens 1 ₁ to the objectand to change the profile of the reflecting surface of the deformablemirror 2 so as to suit to a corresponding state.

Thus, in the optical system of the present invention, when the voltageapplied or the current supplied to the deformable mirror 2 is optimizedin accordance with the zoom state and the distance from the surface ofthe first lens to the object and the profile of the reflecting surfaceof the deformable mirror 2 is changed so as to suit to a correspondingstate, a memory, not shown, is provided with a two-dimensional look-uptable (LUT) storing the zoom state and the distance from the surface ofthe first lens to the object as input information, and the voltageapplied or the current supplied to the deformable mirror 2 correspondingto the input information as output information.

Also, in the description of the present invention to be given below, itis assumed that the distance from the surface of the first lens to theobject is simply referred to as the distance to the object.

Here, examples of the LUT used in the present invention are shown.

Table 1 shows an example of the two-dimensional LUT where the deformablemirror has a single electrode.

TABLE 1 Zoom state Wide-angle Standard Telephoto Distance 10 cm a₁₁ a₁₂a₁₃ to 1 m a₂₁ a₂₂ a₂₃ object ∞ a₃₁ a₃₂ a₃₃

If it is assumed that the zoom states are at wide-angle, standard, andtelephoto positions and the distances to the object are 10 cm, 1 cm, andinfinity, the two-dimensional LUT storing information such as that shownin Table 1 is used. In the LUT, each component a_(mn) (m: the distanceto the object=1–3, and n: the zoom state=1–3) stands for optimum appliedvoltage information in each state.

Table 2 shows another example of the two-dimensional LUT where thedeformable mirror has a plurality of electrodes.

TABLE 2 Zoom state Wide-angle Standard Telephoto Distance 10 cm a₁₁₁a₁₁₂ a₁₁₃ a₁₂₁ a₁₂₂ a₁₂₃ a₁₃₁ a₁₃₂ a₁₃₃ to  1 m a₂₁₁ a₂₁₂ a₂₁₃ a₂₂₁ a₂₂₂a₂₂₃ a₂₃₁ a₂₃₂ a₂₃₃ object ∞ a₃₁₁ a₃₁₂ a₃₁₃ a₃₂₁ a₃₂₂ a₃₂₃ a₃₃₁ a₃₃₂a₃₃₃

If it is assumed that the zoom states are at wide-angle, standard, andtelephoto positions, the distances to the object are 10 cm, 1 cm, andinfinity, and the number of electrodes is 3, the two-dimensional LUTstoring information such as that shown in Table 2 is used. In the LUT,each component a_(mno) (m: the distance to the object=1–3, n: the zoomstate=1–3, and o: the electrode=1–3) stands for optimum applied voltageinformation in each state.

Such two-dimensional LUTs are made, for example, by one of the followingmethods.

The first method is that the deformed profile of the reflecting surfacewhere the voltage is applied or the current is supplied to thedeformable mirror is measured by a contactless measuring device, and iscompared with the design value of the optimum profile of the deformablemirror corresponding to the zoom state and the distance to the object.

Specifically, the deformed profile of the reflecting surface where thevoltage is applied or the current is supplied to the deformable mirror 2is measured by the contactless measuring device such as athree-dimensional profile measuring device using an optical probe, aninterferometer, or a Shack-Hartmann measuring device, and as themeasured value of the deformed profile is compared with the design valueof the optimum profile of the deformable mirror 2 corresponding to thezoom state and the distance to the object, the value of the voltageapplied or the current supplied to the deformable mirror 2 is adjustedso that it coincides with the optical design value of the optimumprofile. The value of the voltage applied or the current supplied to thedeformable mirror 2 where the measured value of the deformed profile iscoincides with the optical design value of the optimum profile is storedin an output information area of the LUT as the value of an optimumvoltage to be applied, or an optimum current to be supplied, to thedeformable mirror 2.

According to the first method, the deformed profile of the deformablemirror itself is measured before the deformable mirror is incorporatedin the optical system, and the voltage applied or the current suppliedto the deformable mirror itself is adjusted so that the deformed profileof the reflecting surface coincides with the optimum profile of thereflecting surface conducted by the optical design. Consequently, anoptical system provided with other optical elements, such as lenses, isnot required.

The deformed profile of the deformable mirror itself is measured, andthus when the deformable mirror is constructed with divided electrodes,the change of the profile relative to the electrodes is easily carriedout and the voltage to be applied, or the current to be supplied, toeach of the electrodes can be determined by intuition (with comparativeease).

Since the deformed profile of the deformable mirror is measured beforethe deformable mirror is incorporated in the optical system to determinethe value of the applied voltage, or the supplied current, adjusted sothat it coincides with the optimum profile of the optical design inaccordance with the deformable mirror, variation in the deformed profiledue to an error caused by the fabrication of the deformable mirror canbe eliminated.

The tolerances of the profile of an optical surface may be ±⅛λ–±10 λ,where λ is the average value of wavelengths of light used, with respectto an ordinary design value, depending on the application. The profileof the optical surface may be measured by a three-dimensional measuringdevice. Alternatively, a variable optical-property optical element maybe incorporated in the optical system to measure the optical propertiessuch as aberration and MTF so that the profile of the optical surface isassumed from acquired optical properties.

The second method is that the sharpness of an image formed by theoptical system after the deformable mirror is incorporated is evaluatedto find a voltage that the sharpness of the formed image is optimized inaccordance with the zoom state and the distance to the object.

Specifically, the voltage is applied or the current is supplied to thedeformable mirror 2 after being incorporated in the optical system, andas the sharpness of the formed image by the optical system is evaluatedin accordance with the zoom state and the distance to the object, thevalue of the voltage applied or the current supplied to the deformablemirror 2 is adjusted. The value of the voltage applied or the currentsupplied to the deformable mirror 2 where the sharpness is optimized isstored in the output information area of the LUT as the value of anoptimum voltage to be applied, or an optimum current to be supplied, tothe deformable mirror 2.

Here, an example of the evaluation of the sharpness is explained withreference to FIG. 6. In this figure, the left-hand diagram shows theacquired image, and the right-hand graph shows the spatial frequencycomponent where image information in the observation area of theacquired image is Fourier-transformed.

For example, the spatial frequency component of the acquired image isevaluated. The observation area of the acquired image (it is hereassumed to be a central portion) is Fourier-transformed, and theintegral value of the frequency component over a threshold (indicated bya hatching portion) is evaluated. This integral value of the frequencycomponent over the threshold is evaluated in accordance with a change ofthe voltage applied or the current supplied, and an image of the largestintegral value is thought of as an image with the best sharpness.

In this case, it is only necessary that a mark, such as a three-barresolution test chart, a bright spot, or a cross line, is used as anobject corresponding to the acquired image and when such marks arelocated at several places in an imaging area and are properly imaged,this image is thought of as the best one.

Since the second method is that after the entire optical system isassembled, the sharpness of an image finally acquired is evaluated,variation in assembly errors of individual optical componentsconstituting the optical system can be eliminated. In addition, the LUTcan be made so that the formed image is optimized. Hence, it isdesirable that the LUT is finally made by the second method.

From the above description, it is ideal that the LUT used in the opticalsystem of the present invention is made in such a way that before theoptical components are incorporated in the optical system, the data ofthe output information (the applied voltage or the supplied current)corresponding to rough input information (the zoom state and thedistance to the object) are secured by the first method, and afterassembly, the data of final fine input and output information arefurnished by the second method.

Also, “the tolerances of the sharpness of the image” in the presentinvention refer to at least ⅘–⅕ the value of the MTF of the design valueat a frequency by the MTF of the optical system, for instance.

Thus, the constructions in which the LUT made by the above methods isused to determine the value of the optimum voltage applied or theoptimum current supplied to the deformable mirror will be describedbelow as the embodiments of the present invention. Also, in each of theembodiments, it is assumed that the reflecting surface of the deformablemirror is conveniently deformed by the application of the voltage.

First Embodiment

FIG. 7 is a block diagram for determining the voltage applied to thedeformable mirror, with reference to the two-dimensional LUT made by theabove methods, in the optical system of the first embodiment of thepresent invention. As shown in FIG. 7, the zoom state and theinformation of the distance to the object are input into atwo-dimensional LUT 10, and voltage information corresponding to theseis input into a voltage control device 11. The voltage control device 11is such that the voltage corresponding to the input is applied to thedeformable mirror 2. In FIG. 7, arrows located on the right side of theLUT 10 are drawn by thicker lines. This means that when the electrodeprovided on the deformable mirror 2 is divided, voltages to be appliedto individual electrodes are different, and thus a plurality of piecesof information are secured. Also, the voltage control device 11 isprovided in the optical system of the present invention.

When the zoom state and the distance to the object are found by a sensoron image formation, the input into the LOUT 10 can be determinedunambiguously by the output information of the sensor. However, when theinformation of one of the zoom state and the distance to the object isunclear, the input into the LUT 10 is fixed with respect to knowninformation, and for unclear information, the input into the LUT 10 mustbe determined in some way.

Thus, in such a case, the input into the LUT 10 is changed in turn toalter the voltage applied to the deformable mirror 2, and the sharpnessof the formed image is evaluated in accordance with this alteration sothat information at a measuring point where the sharpness of the formedimage becomes best in input into the LUT 10. By doing so, the voltageapplied to the deformable mirror 2 can be determined.

When both the zoom state and the distance to the object are unclear, theLUT 10 is input in turn to find full output information stored in theLUT 10, and the voltage applied to the deformable mirror 2 is changed inturn on the basis of acquired output information to evaluate thesharpness of the formed image in accordance with this change so thatinformation at a measuring point where the sharpness of the formed imagebecomes best is set as the input value of the LUT. By doing so, thevoltage applied to the deformable mirror 2 can be determined.

Also, although reference has been made to the case where the variablemirror is used, the present invention is not limited to this and, forexample, a variable focal-length lens may be used instead of thevariable mirror.

When the applied voltage is determined in accordance with the LUT asmentioned above, input information is discrete and thus acquired outputinformation also becomes discrete. When it is assumed that there are nways for the zoom state and m ways for the distance to the object, theoutput information of n×m ways is secured. Since the zoom state and thedistance to the object are discrete here, they must be subdivided formore accurate control. This requires a tedious examination process andcauses a great working cost. Moreover, when the number of dividedelectrodes is k, a wide memory space of n×m×k is required.

Thus, in the present invention, one of the zoom state and the distanceto the object is discretely examined, and for the other, an approximatecurve is found in accordance with this discrete information to falselygive information in succession. Consequently, accurate control can bemade and the memory space can be reduced.

Here, a description will be given of how to find the approximate curvein reference with FIG. 8. It is assumed that measuring results shown inthe figure are obtained with respect to the zoom states (wide-angle,standard, and telephoto positions) and the distances to the object(infinity, 1 m, and 10 cm) at an applied voltage bringing about theoptimum profile (measuring points are indicated by marks □, Δ, and ∘).The approximate equation of a continuous curve passing through themeasuring points is found.

It is assumed that the measuring points are approximated by theapproximate equation of a secondary curve shown in FIG. 8. Coefficientsa₁, b₁, and c₁ (at the telephoto position), a₂, b₂, and c₂ (at thestandard position), and a₃, b₃, and c₃ (at the wide-angle position) ofindividual curves are prestored in an approximate curve memory 12, to bedescribed later, shown in FIG. 9. Also, this approximate curve memory 12is provided in the optical system of the present invention.

Now, reference is made to the case where the approximate curve memorystoring the coefficients of individual curves is used for actual imageformation. In accordance with the information of the zoom state, acorresponding coefficient is first selected through the approximatecurve memory. For example, when the zoom state is wide-angle, thecoefficients a₃, b₃, and c₃ stored in the approximate curve memory areselected. Subsequently, a variable X (X₁ or X₂ in the figure) isdetermined in accordance with the distance to the object. Suchinformation is calculated by an arithmetical unit 13 shown in FIG. 9,and an applied voltage V is finally determined. In this case, althougheach zoom state is discrete, the distance to the object can becontinuously processed. Also, the arithmetical unit 13 is provided inthe optical system of the present invention.

When the distance to the object is unclear, the variable X is changedand the sharpness of the formed image is evaluated in accordance withthis change to find the variable X where the sharpness is highest. Thevariable X is calculated, together with the variable corresponding tothe zoom state, by the arithmetical unit, and thereby the optimumapplied voltage can be determined.

The constructions where the approximate curve is used to find theoptimum applied voltage are shown in FIGS. 9 and 10 as block diagramsfor determining the voltage applied to the deformable mirror in thesecond and third embodiments of the optical system of the presentinvention.

Second Embodiment

The approximate curve information of the zoom state is stored in theapproximate curve memory 12 shown in FIG. 9, and by inputting the zoomstate, one approximate curve, with the distance to the object as avariable, is selected. Furthermore, by inputting the distance to theobject and the approximate curve information into the arithmetical unit13, the information of the optimum applied voltage is determinedunambiguously. According to the second embodiment, therefore, the zoomstate is discrete, but the distance to the object can be continuouslyprocessed.

Third Embodiment

The approximate curve information of the distance to the object isstored in the approximate curve memory 12 shown in FIG. 10, and byinputting the distance to the object, one approximate curve, with thezoom state as a variable, is selected. Furthermore, by inputting thezoom state and the approximate curve information into the arithmeticalunit 13, the information of the optimum applied voltage is determinedunambiguously. According to the third embodiment, therefore, thedistance to the object is discrete, but the zoom state can becontinuously processed.

As the application of this, the construction where both the zoom stateand the distance to the object are expressed by an approximate surfaceis shown in FIG. 11 as a block diagram for determining the voltageapplied to the deformable mirror in the fourth embodiment of the opticalsystem of the present invention.

Fourth Embodiment

Approximate surface information including the approximate curveinformation of the distance to the object and the approximate curveinformation of the zoom state is stored in an approximate surface memory12′ shown in FIG. 11, and a piece of approximate surface information,with the zoom state and the distance to the object as variables, isselected. Furthermore, by inputting the approximate surface informationinto the arithmetical unit 13, the information of the optimum appliedvoltage can be determined unambiguously. According to the fourthembodiment, therefore, both the zoom state and the distance to theobject can be continuously processed.

Also, in the above embodiments, a zoom optical system has beendescribed. However, in a single focus optical system as well, theconstruction for determining the applied voltage that drives thedeformable mirror in the present invention is applicable.

In this case, the input information is the distance to the object andthe output information is the applied voltage, or the supplied current,corresponding to the input information. The LUT, as shown in Table 3 (asingle electrode) or 4 (a plurality of electrodes), listsone-dimensional data. In the present invention, the LUT in this case isreferred to as a one-dimensional LUT.

TABLE 3 Optimum applied voltage Distance 10 cm a₁ to 1 m a₂ object ∞ a₃

TABLE 4 Optimum applied voltage Distance 10 cm a₁₁ a₁₂ a₁₃ to 1 m a₂₁a₂₂ a₂₃ object ∞ a₃₁ a₃₂ a₃₃

When the voltage is applied to the deformable mirror in reference to theone-dimensional LUT, as shown in FIG. 12, the information of thedistance to the object is input into the one-dimensional LUT, and thevoltage information corresponding to this is input into the voltagecontrol device 11. The voltage control device is such that the voltagecorresponding to the input is applied to the deformable mirror 2.

When the approximate curve is used to find the optimum applied voltage,as shown in FIG. 13, one approximate curve, with the distance to theobject as a variable, is selected for the approximate curve memory 12.Moreover, by inputting the information of the distance to the object andthe approximate curve into the arithmetical unit 13, the information ofthe optimum applied voltage is determined unambiguously.

The one-dimensional LUT includes the amount of shift of a focus positioncaused by a change of the distance to the object or zooming as a key.The one-dimensional LUT of such a key, in contrast with thetwo-dimensional LUT including the distance to the object and the zoomstate as a key, has the merits that a memory can be saved and thedeformable mirror can be controlled with a high speed.

In the above embodiments, reference has been made to the optical systemusing the deformable mirror driven by applying the voltage. Similarly,in an optical system using the deformable mirror driven by supplying thecurrent, the information of the optimum supplied current can bedetermined unambiguously through the LUT, through the approximate curvememory 12 and the arithmetical unit 13, or through the approximatesurface memory 12′ and the arithmetical unit 13.

Further, in the above embodiments, reference has been made to theoptical system chiefly using a single deformable mirror. However, anoptical system including a plurality of deformable mirrors is alsoapplicable to the present invention. It is only necessary to controleach of the deformable mirrors by using a corresponding LUT. A variablemirror whose profile is not changed is also applicable to the presentinvention. In the present invention, it is assumed that the variablemirror whose profile is not changed comes into the category of thedeformable mirror.

Still further, in the above embodiments, reference has been made to theoptical system having the deformable mirror. However, in an opticalsystem having a variable focal-length lens as well, the construction fordetermining the applied voltage or the supplied current that drives thedeformable mirror in the present invention is applicable to aconstruction for determining the applied voltage or the supplied currentthat drives the variable focal-length lens.

Fifth Embodiment

FIG. 14 shows the imaging device of the fifth embodiment in the presentinvention. The imaging device of this embodiment includes an opticalsystem 21 having a variable mirror 22, a control electrode 28, a movinglens unit 23, and an encoder 27; an image sensor 24; an image signalprocessing circuit 25; a CPU 26; an amplifier 29; and a driver 30.

The variable mirror 22 and the control electrode 28 have shapes such asthose shown in FIGS. 15A and 15B, and the variable mirror 22 is suchthat, for example, the profile of a mirror surface is changed inaccordance with the amount of voltage applied to the control electrode28. A detailed structure of the variable mirror will be described later.

FIGS. 16A and 16B show schematically arrangements of the optical system21 in the fifth embodiment. In these figures, the control electrode 28and encoder 27 are omitted for convenience.

The optical system 21, as shown in FIGS. 16A and 16B, has a reflectingsurface 115 interposed between a first negative lens unit 130 and asecond positive lens unit 131, arranged in this order from the objectside. The profile of the reflecting surface 115 is changed, and therebythe reflecting surface of the variable mirror 22 changing the focallength is constructed. The optical system is designed so that the secondpositive lens unit 131 is moved along the optical axis and thereby avariable magnification function is exercised. It is assumed that thefunction of such a zoom optical system is referred to as one-lens-unitzoom.

The variable mirror 22 also has a focus function by changing the focallength of the reflecting surface 115. Consequently, there is no need toshift the position of a lens for focusing, and a driving mechanism canbe eliminated, thereby affording the merits of compactness and costreduction. Moreover, the variable mirror 22 has the function of acompensator compensating focus movement for zooming.

When an infinite object point is brought to a focus, the reflectingsurface 115 of the variable mirror 22 is changed to a nearly flat shape,while when the nearest object point is focused, the reflecting surface115 of the variable mirror 22 assumes the concave shape of a free-formedsurface.

In this zoom optical system, the first lens unit 130 is constructed witha single negative lens; the second lens unit 131 with three lenscomponents composed of four lens elements of a positive lens, a cementedlens of a positive lens element and a negative lens element, and anegative lens; and a third lens unit 135 with a single positive lens. Aplane-parallel plate unit 128 interposed between the third lens unit 135and an imaging plane 118 includes filters and glass covers.

The image sensor 24 disposed at the imaging plane 118 has a rectangularlight-receiving surface, a short side of which is parallel with theplane of the paper. This placement causes an asymmetrical direction ofthe reflecting surface 115 of the variable mirror 22 to coincide withthe short side. This is advantageous for correction for aberration.However, if an advantage is offered to the design of a digital camera,the image sensor may be placed so that its long side is parallel withthe plane of the paper.

The reflecting surface 115 of the variable mirror 22 can also be shapedinto such a profile as to compensate the degradation of imagingperformance due to a manufacturing error. Further, the reflectingsurface 115 of the variable mirror 22 can assume such a profile as tocompensate the shift of the focus position due to the manufacturingerror.

Still further, the reflecting surface 115 of the variable mirror 22 canbe shaped into such a profile as to compensate the shift of the focusposition caused by the movement of the second lens unit 131.

As mentioned above, in the variable mirror 22, when the distance to theobject is changed, its ray reflecting function is altered so that theshift of the focus position or the fluctuation of aberration iscompensated. For example, the variable mirror 22 is deformed so thatwhen the distance to the object is changed, the shift of the focusposition or the fluctuation of aberration are compensated.

The magnification of the optical system is changed by introducing,removing, or decentering a part of a lens system, and the shift of thefocus position or the fluctuation of aberration caused thereby may becompensated by the variable mirror 22.

The optical system 21 is designed so that an image height is 2.82 mm,the F-number is 2.77–4.05, the focal length is 4.58–8.94 mm, and thefield angle is 72.8–34.6°.

It is said throughout the whole of the present invention that, ingeneral, the zoom optical system comes into the category of a variablemagnification optical system. However, the term “zoom optical system” issometimes used in the same sense as the variable magnification opticalsystem.

Subsequently, a description is given of the fundamental operation of theimaging device of the fifth embodiment constructed as mentioned above. Azoom operation is first explained. The zoom operation is performed on amanual zoom system by an operator. A signal expressing the position ofthe moving lens unit 23 is detected by the encoder 27, amplified by theamplifier 29, introduced into the CPU 26 after the A/D conversion, andcalculated. In this way, the position of the moving lens unit 23 isfound.

A focus operation is then described. In order to bring about the beststate of focusing on the basis of the position of the moving lens unit23 and the distance to the object, the surface of the variable mirror 22is deformed. A necessary amount of drive of the variable mirror 22 iscalculated, in the CPU, from the information of the position of themoving lens unit 23 and the distance to the object. A voltage requiredto deform the variable mirror 22 by the necessary amount of drive isfound, and a signal such that the voltage is applied to the controlelectrode 28 is output to the driver 30. Whereby, the variable mirror 22is deformed and focusing is performed. The focus operation is thuscompleted.

Here, a photographing operation is explained. A ray of light from theobject is incident on the optical system 21, is reflected by thevariable mirror 22, emerges from the optical system 21 through themoving lens unit 23, and is incident on the image sensor 24 (such as aCCD or CMOS). (Also, in the fifth embodiment, it is assumed that adigital camera is used). An incident ray is converted intophotoelectricity through the image sensor 24 and is changed to anelectric signal. The electric signal is converted into image signal datathrough the image signal processing circuit 25. This image signal isvariously calculated by the instructions of the CPU 26. The imagesignal, after being compression-processed, is output for recordprocessing (for example, Smart Media or Compact Flash (the trademark ofSanDisk Corporation), not shown), or a thinning process (a process ofreducing the number of pixels) is executed for finder indication. Theimage signal may be used for exposure control, focus control, or whitebalance control.

Here, reference is made to a common autofocus system with respect to thefocus control used in the imaging device. In a silver halide filmcamera, the autofocus (AF) system is available in a technique that anobject is irradiated with infrared rays and its reflected light isreceived to calculate the distance and set a lens position (an infraredactive technique); a technique that, by utilizing the characteristicthat a high-frequency component contained in an image signal in which anoptical image formed on the line sensor of a one-dimensional chargecoupled device is converted into electricity increases according to afocusing state, the high-frequency component of the image signal isextracted and a photographic lens is shifted in the direction in whichits level increases (a contrast technique); or a technique that, byutilizing the characteristic that the optical image passing through thephotographic lens is further passed through a separation optical lens (aseparator lens), an acquired optical image is further passed through theseparation optical lens (the separator lens), and a mutual distancebetween acquired optical images changes according to the amount of shiftfrom the focusing state, the distance between the images is detected andthereby the focus position of the photographic lens is calculated toshift the photographic lens (a phase contrast technique). In asingle-lens reflex camera for silver halide films, the latter (the phasecontrast technique) is chiefly used.

Most of video cameras and digital cameras use the technique that thesame image sensor for the purpose of recording is used, a detection areais set at about the middle of an image plane to detect the image signalin the detection area, the high-frequency component of the image signalis extracted, and a photographic lens is shifted in the direction inwhich its level increases (a contrast technique with the image sensor).

Also, the imaging device of the fifth embodiment, not shown in a figure,uses an infrared active AF system as a focus control system (AF).

The imaging device of the fifth embodiment is provided with the look-uptable (LUT) that the amount of voltage (deformable mirror drivingvoltage) required to deform the variable mirror 22 by the necessaryamount of drive is stored in a memory, not shown.

TABLE 5 Table 5 shows the data of the look-up table used in the fifthembodiment. Zoom state Distance Telephoto Standard Wide-angle 10 cm T1S1 W1 1 m T2 S2 W2 ∞ T3 S3 W3

In the LUT, the deformable mirror driving voltage is stored inaccordance with the distance to the object and the zoom state. The LUTis retrieved through the CPU 26, with both the distance to the objectand the zoom state as a key, and thereby one deformable mirror drivingvoltage value can be found. The LUT is retrieved, with one of thedistance to the object and the zoom state as a key, and thereby aplurality of deformable mirror driving voltage values at a correspondingdistance to the object or in a coresponding zoom state can be found.

Each of the data values of the LUT listed in Table 5 is that at apredetermined representative point, and a value between therepresentative points is interpolated by approximating a presetrelational expression. It is assumed that the relation of thisinterpolation is known here. Also, for convenience of explanation, theLUT is constructed, with the number of control electrodes for drivingthe deformable mirror as 1.

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirror 22 in the imaging device ofthe fifth embodiment constructed as mentioned above is described inreference to the flowchart of FIG. 17. When the moving lens unit 23 isoperated (Step S1), its position, that is, the zoom state, is detectedthrough the encoder 27 (Step S2). In the imaging device of the fifthembodiment, the AF is of the infrared active system, and thus thedistance to the object can be calculated (Step S3).

In the imaging device of the fifth embodiment, since both the zoom stateand the distance to the object can be held, the LUT is retrieved, withthe zoom state and the distance to the object as a key, to find avoltage value for driving the variable mirror 22 by a necessary amount(Step S4). For example, as shown in Table 5, when the zoom state istelephoto and the distance to the object is infinite, it is onlynecessary to apply the voltage of T3 to the variable mirror 22. Byapplying this voltage to the control electrode 28, the variable mirror22 is driven (Step S5) and a series of operations are completed.

Sixth Embodiment

FIG. 18 shows the imaging device of the sixth embodiment in the presentinvention. The imaging device of the sixth embodiment, which is amodified example of the fifth embodiment, includes the optical system 21having the variable mirror 22, the control electrode 28, the moving lensunit 23, and a stepping motor 35; the image sensor 24; the image signalprocessing circuit 25; the CPU 26; an amplifier 29; a driver 34; and adriver 30. The zoom operation differs from that of the imaging device ofthe fifth embodiment in FIG. 14.

The zoom operation is performed on an electric zoom system, and when theoperator actuates a zoom lever (not shown), the signal is introducedinto the CPU 26 and is calculated in the CPU so that a signal fordriving the moving lens unit 23 is transmitted to the driver 34.Whereby, the stepping motor 35 is driven. Here, the signal sent to thestepping motor 35 is a pulse signal, and therefore the number of sentpulses and the amount of drive of the moving lens unit 23 are processedat a 1:1 ratio. Hence, in the imaging device of the sixth embodiment,the position of the moving lens unit 23 can be recognized without usingthe encoder 27 shown in FIG. 14. Other constructions, functions, andeffects are the same as those of the fifth embodiment.

Seventh Embodiment

The imaging device of this embodiment has fundamentally the sameconstruction as that of the fifth embodiment of FIG. 14 or the sixthembodiment of FIG. 18. However, the imaging device of the seventhembodiment is different from that of the fifth or sixth embodiment anddoes not use the infrared active AF system as the focus control system(AF). Thus, the distance to the object cannot be immediately held.Alternatively, in the imaging device of the seventh embodiment, acontrast AF system is used as the focus control system (AF).

Here, the contrast AF system used in the present invention is explainedwith reference to FIGS. 19 and 20. In the contrast AF system of thepresent invention, as depicted in FIG. 19, an output signal from theimage sensor (a CCD or CMOS) 24 of FIG. 14 or 18 is converted, in theimage signal processing circuit 25, into a Y signal (a luminancesignal), which is input into the CPU 26. In the CPU 26, after the Ysignal is passed through a HPF (a high band-pass filter) 26 a and isrectified by a rectifier circuit 26 b, a high-frequency component isdetected in a detector circuit 26 c. This high-frequency component isused to perform a control calculation in an arithmetical section 26 d.

In the imaging device of the seventh embodiment, when the variablemirror is driven a little in accordance with a predetermined controlvoltage derived from the LUT, a signal such that the variable mirror 22is shifted in the direction in which the high-frequency componentincreases is sent from the CPU 26 to the driver 30 to drive the variablemirror 22.

This process is continuously repeated, and the high-frequency component,as mentioned above, is detected for calculation with respect to theoutput signal from the image sensor so that a resulting calculated valueis compared with a calculated value obtained immediately before.Consequently, the high-frequency component in the present process ismaximized, and when the variable mirror 22 is further driven, feedbackcontrol is made so that the variable mirror is stopped at the positionof the variable mirror where the high-frequency component is maximizedwhen the high-frequency component in the next process reaches theposition where it is reduced (see FIG. 20). The point where thehigh-frequency component is maximized is a focusing position.

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirror 22 in the imaging device ofthe seventh embodiment constructed as mentioned above is described inreference to the flowchart of FIG. 21. When the moving lens unit 23 isoperated (Step S11), its position, that is, the zoom state, is detectedthrough the encoder 27 (Step S12). In the imaging device of the seventhembodiment, the AF does not use the active system, and thus the distanceto the object cannot be directly found. Hence, in the imaging device ofthe seventh embodiment, the LUT is retrieved, with the zoom state as akey (Step S13), and in accordance with a plurality of voltage values fordriving the variable mirror 22 which are column data corresponding tothe zoom state in this case (for example, voltage values of T1, T2, andT3 where the zoom state is telephoto in Table 5), the operation of thecontrast AF system is performed (Step S14). At the position where thehigh-frequency component is maximized, the drive of the variable mirror22 is completed.

Eighth Embodiment

FIG. 22 shows the imaging device of the eighth embodiment in the presentinvention. The imaging device of this embodiment has a fundamentalconstruction in which the encoder 27 and the amplifier 29 are excludedfrom the construction of the fifth embodiment of FIG. 14. Specifically,the encoder or the stepping motor is not mounted to the moving lens unit23. The infrared active AF system is not used as the focus controlsystem (AF). Alternatively, in the imaging device of the eighthembodiment, like the seventh embodiment, the contrast AF system is usedas the focus control system (AF).

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirror 22 in the imaging device ofthe eighth embodiment constructed as mentioned above is described inreference to the flowchart of FIG. 23. The zoom operation is firstoperated (Step S21). However, the moving lens unit 23 is not providedwith the encoder, and thus the zoom state is not detected.

Since the AF of the eighth embodiment does not use the active system,the distance to the object cannot be directly found. Consequently, boththe zoom state and the distance cannot be calculated. Thus, in theimaging device of the eighth embodiment, the LUT is retrieved, with aproper zoom state and distance to the object as a key (Step S22), anddata of its periphery (for example, in order ofT1→T2→T3→S1→S2→S3→W1→W2→W3 in Table 5) are input in succession toperform the operation of the contrast AF (Step S23). At the positionwhere the high-frequency component is maximized, the drive of thevariable mirror is completed.

Ninth Embodiment

The imaging device of this embodiment has fundamentally the sameconstruction as that of the eighth embodiment of FIG. 22. However, theimaging device of the ninth embodiment, unlike that of the eighthembodiment, the infrared active AF system is used as the focus controlsystem (AF). As such, the distance to the object can be heldimmediately.

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirror 22 in the imaging device ofthe ninth embodiment constructed as mentioned above is described inreference to the flowchart of FIG. 24. The zoom operation is firstoperated (Step S31). However, the moving lens unit 23 is not providedwith the encoder, and thus the zoom state is not detected.

Since the AF of the eighth embodiment uses the infrared active system,the distance to the object can be calculated (Step S32). Thus, in theimaging device of the ninth embodiment, the LUT is retrieved, with thedistance to the object as a key (Step S33), and in accordance with aplurality of voltage values for driving the variable mirror 22 which arerow data corresponding to the distance to the object in this case (forexample, voltage values of T3, S3, and W3 where the distance to theobject is infinite in Table 5), the operation of the contrast AF systemis performed (Step S34). At the position where the high-frequencycomponent is maximized, the drive of the variable mirror 22 iscompleted.

Tenth Embodiment

FIG. 25 shows the imaging device of the tenth embodiment in the presentinvention. The imaging device of the tenth embodiment, as shown in FIG.25, has the construction that a variable mirror 31, a control electrode32, and a driver 33 are added to the construction of the fifthembodiment in FIG. 14, and is different from the imaging device of thefifth embodiment in that two variable mirrors 22 and 31 are used anddriven in the variable magnification and focus operations.

FIGS. 26A and 26B show schematically arrangements of an optical system21′ in the tenth embodiment. In these figures, the control electrodes 28and 32 and encoder 27 are omitted for convenience.

The optical system 21, as shown in FIGS. 16A and 16B, has the firstvariable mirror 31 placed on the object side of an rotationallysymmetrical lens system including a front lens unit 125 with negativepower composed of a cemented doublet and a rear lens unit 126 composedof a double cemented lens and a single lens, with a stop 124 betweenthem, and the second variable mirror 22 interposed between the imagingplane 118 and the lens system so that the aspherical profiles ofreflecting surfaces 116 and 115 of the two variable mirrors are changedin association with each other and thereby zooming can be performedtogether with the movement of the lens units 125 and 126. The opticalsystem may be constructed so that at least one of the variable mirrorscontributes to the magnification change of the optical system. There arethe merits that, by using the two variable mirrors as in this example,correction for aberration is facilitated and the amount of deformationof one variable mirror can be reduced.

By chiefly using the spherical surface for each lens, without using thefree-formed surface, and using a rotationally symmetrical asphericalsurface for each of the reflecting surfaces surfaces 116 and 115 of thevariable mirrors 31 and 22, a variable focal-length objective opticalsystem for digital cameras is constructed. However, each of thereflecting surfaces 116 and 115 may be configured as the free-formedsurface or a rotationally asymmetrical aspherical surface. This isadvantageous for correction for aberration.

The optical system 21′ is designed so that the image height is 2 mm, theF-number is 3.1–3.5, and the focal length is 6.76–8.73 mm. FIGS. 26A and26B are an example of the one-lens-unit zoom in which a plurality ofvariable mirrors are used.

Subsequently, a description is given of the fundamental operation of theimaging device of the tenth embodiment constructed as mentioned above. Azoom operation is first explained. The zoom operation is performed on amanual zoom system by an operator. A signal expressing the position ofthe moving lens unit 23 is detected by the encoder 27, amplified by theamplifier 29, introduced into the CPU 26 after the A/D conversion, andcalculated. In this way, the position of the moving lens unit 23 isfound. The moving lens unit 23 corresponds to the lens units 125 and 126of FIGS. 26A and 26B, and the lens units 125 and 126 in this case areintegrally moved when the magnification is changed.

The focus operation is then described. In order to bring about the beststate of focusing on the basis of the position of the moving lens unit23 and the distance to the object, the surfaces of the variable mirrors31 and 22 are deformed. Necessary amounts of drive of the variablemirrors 31 and 22 are calculated, in the CPU, from the information ofthe position of the moving lens unit 23 and the distance to the object.Voltages required to deform the variable mirrors 31 and 22 by thenecessary amounts of drive are found, and signals such that the voltagesare applied to the control electrodes 32 and 28 are output to thedrivers 33 and 30. Whereby, the variable mirrors 31 and 22 are deformedand focusing is performed. The focus operation is thus completed.

Here, the photographing operation is explained. A ray of light from theobject is incident on the optical system 21′, is reflected by thevariable mirrors 31 and 22, emerges from the optical system 21′ throughthe moving lens unit 23, and is incident on the image sensor 24 (such asa CCD or CMOS). (Also, in the tenth embodiment, it is assumed that adigital camera is used). An incident ray is converted intophotoelectricity through the image sensor 24 and is changed to anelectric signal. The electric signal is converted into image signal datathrough the image signal processing circuit 25. This image signal isvariously calculated by the instructions of the CPU 26. The imagesignal, after being compression-processed, is output for recordprocessing (for example, Smart Media or Compact Flash (the trademark ofSanDisk Corporation), not shown), or a thinning process (a process ofreducing the number of pixels) is executed for finder indication. Theimage signal may be used for exposure control, focus control, or whitebalance control.

The imaging device of the tenth embodiment is designed so that theinfrared active AF system, not shown, is used as the focus controlsystem (AF). The contrast AF system may be used.

The imaging device of the tenth embodiment is provided with the look-uptable (LUT) that the amounts of voltages (deformable mirror drivingvoltages) required to deform the variable mirrors 22 and 31 by thenecessary amounts of drive are stored in a memory, not shown.

TABLE 6 Table 6 shows the data of the look-up table used in the tenthembodiment. Zoom state Telephoto Standard Wide-angle 1st 2nd 1st 2nd 1st2nd Distance mirror mirror mirror mirror mirror mirror 10 cm T11 T21 S11S21 W11 W21  1 m T12 T22 S12 S22 W12 W22 ∞ T13 T23 S13 S23 W13 W23

In the LUT, the deformable mirror driving voltages of the first andsecond variable mirrors 31 and 22 are stored in accordance with thedistance to the object and the zoom state. The LUT is retrieved throughthe CPU 26, with both the distance to the object and the zoom state as akey, and thereby one deformable mirror driving voltage value can befound with respect to each of the first and second variable mirrors 31and 22. The LUT is retrieved, with one of the distance to the object andthe zoom state as a key, and thereby a plurality of deformable mirrordriving voltage values at a corresponding distance to the object or in acoresponding zoom state can be found with respect to each of the firstand second variable mirrors 31 and 22.

Each of the data values of the LUT listed in Table 6 is that at apredetermined representative point, and a value between therepresentative points is interpolated by approximating a presetrelational expression. It is assumed that the relation of thisinterpolation is known here. Also, for convenience of explanation, theLUT is constructed, with the number of control electrodes for drivingeach deformable mirror as 1.

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirrors 31 and 22 in the imagingdevice of the tenth embodiment constructed as mentioned above isdescribed in reference to the flowchart of FIG. 17 as in the fifthembodiment. When the moving lens unit 23 is operated (Step S1), itsposition, that is, the zoom state, is detected through the encoder 27(Step S2). In the imaging device of the tenth embodiment, the AF is ofthe infrared active system, and thus the distance to the object can becalculated (Step S3).

In the imaging device of the tenth embodiment, since both the zoom stateand the distance to the object can be held, the LUT is retrieved, withthe zoom state and the distance to the object as a key, to find voltagevalues for driving the variable mirrors 31 and 22 by necessary amounts(Step S4). For example, as shown in Table 6, when the zoom state istelephoto and the distance to the object is infinite, it is onlynecessary to apply the voltage of T13 to the variable mirror 31 and thevoltage of T23 to the variable mirror 22. By applying these voltages tothe control electrodes 32 and 28, the variable mirrors 31 and 22 aredriven (Step S5) and a series of operations are completed.

In the embodiment of FIG. 25, the long side of the image sensor may beparallel with the plane of the paper. That is, the long side of theimage sensor may be parallel with the plane of incidence of an axial rayon the variable mirror. It is for this reason that the ability tocorrect aberration is excellent because of the two variable mirrors.That the orientation of the image sensor is chosen at will isadvantageous for the design of the digital camera.

Eleventh Embodiment

FIG. 27 shows the imaging device of the eleventh embodiment in thepresent invention. The imaging device of this embodiment, which is amodified example of the tenth embodiment, includes the optical system21′ having the first and second variable mirrors 31 and 22, the controlelectrodes 32 and 28, the moving lens unit 23, and the stepping motor35; the image sensor 24; the image signal processing circuit 25; the CPU26; the driver 34; and drivers 33 and 30. The zoom operation differsfrom that of the imaging device of the tenth embodiment in FIG. 25.

The zoom operation is performed on an electric zoom system, and when theoperator actuates a zoom lever (not shown), the signal is introducedinto the CPU 26 and is calculated in the CPU so that a signal fordriving the moving lens unit 23 is transmitted to the driver 34.Whereby, the stepping motor 35 is driven. Here, the signal sent to thestepping motor 35 is a pulse signal, and therefore the number of sentpulses and the amount of drive of the moving lens unit 23 are processedat a 1:1 ratio. Hence, in the imaging device of the eleventh embodiment,the position of the moving lens unit 23 can be recognized without usingthe encoder 27 shown in FIG. 25. Other constructions, functions, andeffects are the same as those of the tenth embodiment.

Each of the tenth and eleventh embodiments may be designed so that themoving lens unit 23 is fixed and the magnification change and focusing,the focus shift involved in the magnification change, and thefluctuation of aberration are compensated by only deforming the twovariable mirrors. In this case, the position detecting means of themoving lens unit is not required, and it is only necessary to study theLUT corresponding to the zoom state indicated by the operator and drivethe two variable mirrors into optimum shapes. Such a variable mirrorcontrol technique can be utilized for other embodiments and is alsoapplicable to the embodiment using the variable focal-length lensinstead of the variable mirror.

Twelfth Embodiment

The imaging device of this embodiment has fundamentally the sameconstruction as that of the tenth embodiment of FIG. 25 or the eleventhembodiment of FIG. 27. However, the imaging device of the twelfthembodiment is different from that of the tenth or eleventh embodimentand does not use the infrared active AF system as the focus controlsystem (AF). Thus, the distance to the object cannot be immediatelyheld. Alternatively, in the imaging device of the twelfth embodiment,the contrast AF system is used as the focus control system (AF).

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirrors 31 and 22 in the imagingdevice of the twelfth embodiment constructed as mentioned above isdescribed in reference to FIG. 21 as in the seventh embodiment. When themoving lens unit 23 is operated (Step S11), its position, that is, thezoom state, is detected through the encoder 27 (Step S12). In theimaging device of the twelfth embodiment, the AF does not use the activesystem, and thus the distance to the object cannot be directly found.Hence, in the imaging device of the twelfth embodiment, the LUT isretrieved, with the zoom state as a key (Step S13), and in accordancewith a plurality of voltage values for driving the variable mirrors 31and 22 which are row data corresponding to the zoom state in this case(for example, voltage values of T11 and T21; T12 and T22; and T13 andT23 where the zoom state is telephoto in Table 6), the operation of thecontrast AF system is performed (Step S14). At the position where thehigh-frequency component is maximized, the drive of the variable mirrors31 and 22 is completed.

Thirteen Embodiment

FIG. 28 shows the imaging device of the thirteenth embodiment in thepresent invention. The imaging device of this embodiment has afundamental construction in which the encoder 27 and the amplifier 29are excluded from the construction of the tenth embodiment of FIG. 25.Specifically, the encoder or the stepping motor is not mounted to themoving lens unit 23. The infrared active AF system is not used as thefocus control system (AF). Alternatively, in the imaging device of thethirteenth embodiment, like the twelfth embodiment, the contrast AFsystem is used as the focus control system (AF).

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirrors 31 and 22 in the imagingdevice of the thirteenth embodiment constructed as mentioned above isdescribed in reference to FIG. 23 as in the eighth embodiment. The zoomoperation is first operated (Step S21). However, the moving lens unit 23is not provided with the encoder, and thus the zoom state is notdetected.

Since the AF of the thirteenth embodiment does not use the activesystem, the distance to the object cannot be directly found.Consequently, both the zoom state and the distance cannot be calculated.Thus, in the imaging device of the thirteenth embodiment, the LUT isretrieved, with a proper zoom state and distance to the object as a key(Step S22), and data of its periphery (for example, in order of T11 andT21→T12 and T22→T13 and T23→S11 and S21→S12 and S22→S13 and S23→W11 andW21→W12 and W22→W13 and W23 in Table 6) are input in succession toperform the operation of the contrast AF (Step S23). At the positionwhere the high-frequency component is maximized, the drive of thevariable mirrors is completed.

Fourteenth Embodiment

The imaging device of this embodiment has fundamentally the sameconstruction as that of the thirteenth embodiment of FIG. 28. However,the imaging device of the fourteenth embodiment, unlike that of thethirteenth embodiment, the infrared active AF system is used as thefocus control system (AF). As such, the distance to the object can beheld immediately.

Subsequently, a control process from the operation of the moving lensunit 23 to the drive of the variable mirrors 31 and 22 in the imagingdevice of the ninth embodiment constructed as mentioned above isdescribed in reference to FIG. 24 as in the ninth embodiment. The zoomoperation is first operated (Step S31). However, the moving lens unit 23is not provided with the encoder, and thus the zoom state is notdetected. Since the AF of the fourteenth embodiment uses the infraredactive system, the distance to the object can be calculated (Step S32).

Thus, in the imaging device of the fourteenth embodiment, the LUT isretrieved, with the distance to the object as a key (Step S33), and inaccordance with a plurality of voltage values for driving the first andsecond variable mirrors 31 and 22 which are row data corresponding tothe distance to the object in this case (for example, voltage values ofT13 and T23, S13 and S23, and W13 and W23 where the distance to theobject is infinite in Table 6), the operation of the contrast AF systemis performed (Step S34). At the position where the high-frequencycomponent is maximized, the drive of the variable mirrors 31 and 22 iscompleted.

In the above description, each of the reflecting surfaces of thevariable mirrors shown in FIGS. 14–28 is shaped into a convex form, butit may, of course, be concave. Also, although each of the variablemirrors is driven on the voltage, it may be driven on the current, andthis case also falls within the scope of the present invention.

In the above embodiments, reference has been made to the case where thevariable mirror is used, but, for example, even when a variablefocal-length lens 22′, as shown in FIGS. 29–31, is used instead of thevariable mirror, the same effect can be obtained.

In the disclosure so far, reference has been made to examples where thelook-up table is chiefly used to control the variable optical-propertyoptical element. However, the look-up table need not necessarily beused. It is only necessary to provide some control informationcontrolling the variable optical-property optical element in the opticalapparatus, and such a case also falls within the scope of the presentinvention.

Subsequently, a description will be given of the examples of structuresof the variable mirror, the variable focal-length lens, and the likewhich are applicable to the present invention.

A deformable mirror whose reflecting surface is deformed and a variablefocal-length mirror whose reflecting surface is not deformed, such asthat of FIG. 57 to be described later, fall under the class of thevariable mirror.

FIG. 32 shows a Keplerian finder for a digital camera using a variableoptical-property mirror as the variable mirror used in the imagingdevice of the present invention. It can, of course, be used for a silverhalide film camera. Reference is first made to a variableoptical-property mirror 409.

The variable optical-property mirror 409 refers to an optical-propertydeformable mirror (which is hereinafter simply called the deformablemirror) comprised of a thin film (reflecting surface) 409 a coated withaluminum and a plurality of electrodes 409 b. Reference numeral 411denotes a plurality of variable resistors connected to the electrodes409 b; 412 denotes a power supply connected between the thin film 409 aand the electrodes 409 b through the variable resistors 411 and a powerswitch 413; 414 denotes an arithmetical unit for controlling theresistance values of the variable resistors 411; and 415, 416, and 417denote a temperature sensor, a humidity sensor, and a range sensor,respectively, connected to the arithmetical unit 414, which are arrangedas shown in the figure to constitute one optical apparatus.

Each of the surfaces of an objective lens 902, an eyepiece 901, a prism404, an isosceles rectangular prism 405, a mirror 406, and thedeformable mirror 409 need not necessarily be planar, and may have anyshape such as a spherical or rotationally symmetrical asphericalsurface; a spherical, planar, or rotationally symmetrical asphericalsurface which is decentered with respect to the optical axis; anaspherical surface with symmetrical surfaces; an aspherical surface withonly one symmetrical surface; an aspherical surface with no symmetricalsurface; a free-formed surface; a surface with a nondifferentiable pointor line; etc. Moreover, any surface which has some effect on light, suchas a reflecting or refracting surface, is satisfactory. In general, sucha surface is hereinafter referred as to an extended surface.

The thin film 409 a, like a membrane mirror set forth, for example, in“Handbook of Microlithography, Micromachining and Microfabrication”, byP. Rai-Choudhury, Volume 2: Micromachining and Microfabrication, p. 495,FIG. 8.58, SPIE PRESS, or Optics Communication, Vol. 140, pp. 187–190,1997, is such that when the voltage is applied across the plurality ofelectrodes 409 b, the thin film 409 a is deformed by the electrostaticforce and its surface profile is changed. Whereby, not only can focusingbe adjusted to the diopter of an observer, but also it is possible tosuppress deformations and changes of refractive indices, caused bytemperature and humidity changes of the lenses 902 and 901 and/or theprism 404, the isosceles rectangular prism 405, and the mirror 406, orthe degradation of imaging performance by the expansion and deformationof a lens frame and assembly errors of parts, such as optical elementsand frames. In this way, a focusing adjustment and correction foraberration produced by the focusing adjustment can be always properlymade.

Also, it is only necessary that the shape of the electrodes 409 b, forexample, as shown in FIGS. 34 and 35, is selected in accordance with thedeformation of the thin film 409 a.

According to the embodiment, light from an object is refracted by theentrance and exit surfaces of the objective lens 902 and the prism 404,and after being reflected by the deformable mirror 409, is transmittedthrough the prism 404. The light is further reflected by the isoscelesrectangular prism 405 (in FIG. 32, a mark + on the optical pathindicates that a ray of light travels toward the back side of the planeof the page), and is reflected by the mirror 406 to enter the eyethrough the eyepiece 901. As mentioned above, the lenses 902 and 901,the prisms 404 and 405, and the deformable mirror 409 constitute theobserving optical system of the optical apparatus in the embodiment. Thesurface profile and thickness of each of these optical elements isoptimized and thereby aberration can be minimized. When lithography isused to fabricate the deformable mirror 409, the deformable mirror 409with a high degree of accuracy is obtained.

Specifically, the configuration of the thin film 409 a, as thereflecting surface, is controlled in such a way that the resistancevalues of the variable resistors 411 are changed by signals from thearithmetical unit 414 to optimize imaging performance. Signalscorresponding to ambient temperature and humidity and the distance tothe object are input into the arithmetical unit 414 from the temperaturesensor 415, the humidity sensor 416, and the range sensor 417. In orderto compensate for the degradation of imaging performance due to theambient temperature and humidity and the distance to the object inaccordance with these input signals, the arithmetical unit 414 outputssignals for determining the resistance values of the variable resistors411 so that voltages by which the configuration of the thin film 409 ais determined are applied to the electrodes 409 b. Thus, since the thinfilm 409 a is deformed with the voltages applied to the electrodes 409b, that is, the electrostatic force, it assumes various shapes includingan aspherical surface, according to circumstances. The range sensor 417need not necessarily be used, and in this case, it is only necessarythat an imaging lens 403 of the digital camera is moved so that ahigh-frequency component of an image signal from a solid-state imagesensor 408 is roughly maximized, and the object distance is calculatedfrom this position so that an observer's eye is able to focus upon theobject image by deforming the deformable mirror.

When the thin film 409 a is made of synthetic resin, such as polyimide,it can be considerably deformed even at a low voltage, which isadvantageous. Also, the prism 404 and the deformable mirror 409 can beintegrally configured into a unit. Although not shown in the figure, thesolid-state image sensor 408 may be constructed integrally with thesubstrate of the deformable mirror 409 by a lithography process.

When each of the lenses 901 and 902, the prisms 404 and 405, and themirror 406 is configured by a plastic mold, an arbitrary curved surfaceof a desired configuration can be easily obtained and its fabrication issimple. In the imaging device of the embodiment, the lenses 902 and 901are arranged separately from the prism 404. However, if the prisms 404and 405, the mirror 406, and the deformable mirror 409 are designed sothat aberration can be eliminated without providing the lenses 902 and901, the prisms 404 and 405 and the deformable mirror 409 will beconfigured as one optical block, and the assembly is facilitated. Partsor all of the lenses 902 and 901, the prisms 404 and 405, and the mirror406 may be made of glass. By doing so, an imaging device with a higherdegree of accuracy is obtained.

Also, although in FIG. 32 the arithmetical unit 414, the temperaturesensor 415, the humidity sensor 416, and the range sensor 417 areprovided so that the deformable mirror 409 compensates for the changesof the temperature, the humidity, and the object distance, the presentinvention is not limited to this construction. That is, the arithmeticalunit 414, the temperature sensor 415, the humidity sensor 416, and therange sensor 417 may be eliminated so that the deformable mirror 409compensates for only a change of an observer's diopter.

FIG. 33 shows another embodiment of the deformable mirror 409 used asthe variable mirror in the present invention. In this embodiment, apiezoelectric element 409 c is interposed between the thin film 409 aand the electrodes 409 b, and these are placed on a support 423. Avoltage applied to the piezoelectric element 409 c is changed inaccordance with the individual electrodes 409 b, and thereby thepiezoelectric element 409 c causes expansion or contraction which ispartially different so that the shape of the thin film 409 a can bechanged. The configuration of the electrodes 409 b may be selected inaccordance with the deformation of the thin film 409 a. For example, asillustrated in FIG. 34, it may have a concentric division pattern, or asin FIG. 35, it may be a rectangular division pattern. As other patterns,proper configurations can be chosen. In FIG. 33, reference numeral 424represents a shake sensor connected to the arithmetical unit 414. Theshake sensor 424, for example, detects the shake of a digital camera andchanges the voltages applied to the electrodes 409 b through thearithmetical unit 414 and the variable resistors 411 in order to deformthe thin film 409 a to compensate for the blurring of an image caused bythe shake. At this time, the signals from the temperature sensor 415,the humidity sensor 416, and range sensor 417 are taken into accountsimultaneously, and focusing and compensation for temperature andhumidity are performed. In this case, stress is applied to the thin film409 a by the deformation of the piezoelectric element 409 c, and henceit is good practice to design the thin film 409 a so that it has amoderate thickness and a proper strength.

FIG. 36 shows still another embodiment of the deformable mirror 409 usedas the variable mirror in the present invention. This embodiment has thesame construction as the embodiment of FIG. 33 with the exception thattwo piezoelectric elements 409 c and 409 c′ are interposed between thethin film 409 a and the electrodes 409 b and are made with substanceshaving piezoelectric characteristics which are reversed in direction.Specifically, when the piezoelectric elements 409 c and 409 c′ are madewith ferroelectric crystals, they are arranged so that their crystalaxes are reversed in direction with respect to each other. In this case,the piezoelectric elements 409 c and 409 c′ expand or contract in areverse direction when voltages are applied, and thus there is theadvantage that a force for deforming the thin film 409 a becomesstronger than in the embodiment of FIG. 33 and as a result, the shape ofthe mirror surface can be considerably changed.

For substances used for the piezoelectric elements 409 c and 409 c′, forexample, there are piezoelectric substances such as barium titanate,Rochelle salt, quartz crystal, tourmaline, KDP, ADP, and lithiumniobate; polycrystals or crystals of the piezoelectric substances;piezoelectric ceramics such as solid solutions of PbZrO₃ and PbTiO₃;organic piezoelectric substances such as PVDF; and other ferroelectrics.In particular, the organic piezoelectric substance has a small value ofYoung's modulus and brings about a considerable deformation at a lowvoltage, which is favorable. When the piezoelectric elements 409 c and409 c′ are used, it is also possible to properly deform the thin film409 a in the above embodiment if their thicknesses are made uneven.

For materials of the piezoelectric elements 409 c and 409 c′,high-polymer piezoelectrics such as polyurethane, silicon rubber,acrylic elastomer, PZT, PLZT, and PVDF; vinylidene cyanide copolymer;and copolymer of vinylidene fluoride and trifluoroethylene are used.

The use of an organic substance, synthetic resin, or elastomer, having apiezoelectric property, brings about a considerable deformation of thesurface of the deformable mirror, which is favorable.

When an electrostrictive substance, for example, acrylic elastomer orsilicon rubber, is used for the piezoelectric element 409 c shown inFIGS. 33 and 36, the piezoelectric element 409 c, as indicated by abroken line in FIG. 33, may be constructed by cementing anothersubstrate 409 c-1 to an electrostrictive substance 409 c-2.

FIG. 37 shows another embodiment of the deformable mirror 409 used asthe variable mirror in the present invention. The deformable mirror 409of this embodiment is designed so that the piezoelectric element 409 cis sandwiched between the thin film 409 a and an electrode 409 d, andvoltages are applied between the thin film 409 a and the electrode 409 dthrough a driving circuit 425′ controlled by the arithmetical unit 414.Furthermore, voltages are also applied to the electrodes 409 b providedon the support 423, through driving circuits 425 controlled by thearithmetical unit 414. In this embodiment, therefore, the thin film 409a can be doubly deformed by electrostatic forces due to the voltagesapplied between the thin film 409 a and the electrode 409 d and appliedto the electrodes 409 b. There are advantages that various deformationpatterns can be provided and the response is quick, compared with any ofthe above embodiments.

By changing the signs of the voltages applied between the thin film 409a and the electrode 409 d, the deformable mirror can be deformed into aconvex or concave surface. In this case, a considerable deformation maybe performed by a piezoelectric effect, while a slight shape change maybe carried out by the electrostatic force. Alternatively, thepiezoelectric effect may be used for the deformation of the convexsurface, while the electrostatic force may be used for the deformationof the concave surface. Also, the electrode 409 d may be constructed asa plurality of electrodes like the electrodes 409 b. This condition isshown in FIG. 37. In the present invention, all of the piezoelectriceffect, the electrostrictive effect, and electrostriction are generallycalled the piezoelectric effect. Thus, it is assumed that theelectrostrictive substance comes under the class of the piezoelectricsubstance.

FIG. 38 shows another embodiment of the deformable mirror 409 used asthe variable mirror according to the present invention. The deformablemirror 409 of this embodiment is designed so that the shape of thereflecting surface can be changed by utilizing an electromagnetic force.A permanent magnet 426 mounted and fixed on a bottom surface inside thesupport 423, and the periphery of a substrate 409 e made with siliconnitride or polyimide is mounted on the top surface thereof. The thinfilm 409 a consisting of the coating of metal, such as aluminum, isdeposited on the surface of the substrate 409 e, thereby constitutingthe deformable mirror 409. Below the substrate 409 e, a plurality ofcoils 427 are arranged and connected to the arithmetical unit 414through the driving circuits 428. In accordance with output signals fromthe arithmetical unit 414 corresponding to changes of the optical systemobtained at the arithmetical unit 414 by signals from the sensor 415,416, 417, and 424, proper electric currents are supplied from thedriving circuits 428 to the coils 427. At this time, the coils 427 arerepelled or attracted by the electromagnetic force with the permanentmagnet 426 to deform the substrate 409 e and the thin film 409 a.

In this case, a different amount of current can also be caused to flowthrough each of the coils 427. A single coil 427 may be used, and thepermanent magnet 426 may be provided on the substrate 409 e so that thecoils 427 are arranged on the bottom side in the support 423. It isdesirable that the coils 427 are fabricated by a lithography process. Aferromagnetic core (iron core) may be encased in each of the coils 427.

In this case, each of the coils 427, as illustrated in FIG. 39, can bedesigned so that a coil density varies with place and thereby a desireddeformation is brought to the substrate 409 e and the thin film 409 a. Asingle coil 427 may be used, and a ferromagnetic core (iron core) may beencased in each of the coils 427.

FIG. 40 shows another embodiment of the deformable mirror 409 used asthe variable mirror according to the present invention. In thedeformable mirror 409 of this embodiment, the substrate 409 e is madewith a ferromagnetic such as iron, and the thin film 409 a as areflecting film is made with aluminum. In this case, since the thin filmcoils need not be used, the structure is simple and the manufacturingcost can be reduced. If the power switch 413 is replaced with achangeover and power on-off switch, the directions of currents flowingthrough the coils 427 can be changed, and the configurations of thesubstrate 409 e and the thin film 409 a can be changed at will. FIG. 41shows an array of the coils 427 in this embodiment, and FIG. 42 showsanother array of the coils 427. These arrays are also applicable to theembodiment of FIG. 38. FIG. 43 shows an array of the permanent magnets426 suitable for the array of the coils of FIG. 42 in the embodiment ofFIG. 38. Specifically, when the permanent magnets 426, as shown in FIG.43, are radially arranged, a delicate deformation can be provided to thesubstrate 409 e and the thin film 409 a in contrast with the embodimentof FIG. 38. As mentioned above, when the electromagnetic force is usedto deform the substrate 409 e and the thin film 409 a (in theembodiments of FIGS. 38 and 40), there is the advantage that they can bedriven at a lower voltage than in the case where the electrostatic forceis used.

Some embodiments of the deformable mirror have been described, but asshown in FIG. 37, at least two kinds of forces may be used in order tochange the shape of the deformable mirror. Specifically, at least two ofthe electrostatic force, electromagnetic force, piezoelectric effect,magnetrostriction, pressure of a fluid, electric field, magnetic field,temperature change, and electromagnetic wave, may be used simultaneouslyto deform the deformable mirror. That is, when at least two differentdriving techniques are used to make the variable optical-propertyoptical element, a considerable deformation and a slight deformation canbe realized simultaneously and a mirror surface with a high degree ofaccuracy can be obtained.

FIG. 44 shows an imaging system which uses the deformable mirror 409 asthe variable mirror applicable to the optical apparatus, in anotherembodiment of the present invention, and which is used, for example, ina digital camera of a cellular phone, a capsule endoscope, an electronicendoscope, a digital camera for personal computers, or a digital camerafor PDAs.

In the imaging system of this embodiment, one imaging unit 104 isconstructed with the deformable mirror 409, the lens 902, thesolid-state image sensor 408, and a control system 103. In the imagingunit 104 of the embodiment, light from an object passing through thelens 902 is condensed by the deformable mirror 409 and is imaged on thesolid-state image sensor 408. The deformable mirror 409 is a kind ofvariable optical-property optical element and is also referred to as thevariable focal-length mirror.

According to this embodiment, even when the object distance is changed,the deformable mirror 409 is deformed and thereby the object can bebrought into a focus. The embodiment need not use the motor to move thelens and excels in compact and lightweight design and low powerconsumption. The imaging unit 104 can be used in any of the embodimentsas the imaging system of the present invention. When a plurality ofdeformable mirrors 409 are used, a zoom or variable magnificationimaging system or optical system can be constructed.

In FIG. 44, an example of a control system which includes the boostingcircuit of a transformer using coils in the control system 103 is cited.When a laminated piezoelectric transformer is particularly used, acompact design is achieved. The boosting circuit can be used in thedeformable mirror or the variable focal-length lens of the presentinvention which uses electricity, and is useful in particular for thedeformable mirror or the variable focal-length lens which utilizes theelectrostatic force or the piezoelectric effect.

FIG. 45 shows a deformable mirror 188 in which a fluid 161 is taken inand out by a micropump 180 to deform a mirror surface, in anotherembodiment of the variable mirror according to the present invention.According to this embodiment, there is the merit that the mirror surfacecan be considerably deformed.

The micropump 180 is a small-sized pump, for example, made by amicromachining technique and is constructed so that it is operated withan electric power. As examples of pumps made by the micromachiningtechnique, there are those which use thermal deformations, piezoelectricsubstances, and electrostatic forces.

FIG. 46 shows an example of a micropump applicable to the variablemirror used in the imaging device of the present invention. In themicropump 180 of the embodiment, a vibrating plate 181 is vibrated bythe electrostatic force or the electric force of the piezoelectriceffect. In this figure, a case where the vibrating plate is vibrated bythe electrostatic force is shown and reference numerals 182 and 183represent electrodes. Dotted lines indicate the vibrating plate 181where it is deformed. When the vibrating plate 181 is vibrated, twovalves 184 and 185 are opened and closed to feed the fluid 161 from theright to the left.

In the deformable mirror 188 of this embodiment, the reflecting film 181is deformed into a concave or convex surface in accordance with theamount of the fluid 161, and thereby functions as the deformable mirror.The deformable mirror 188 is driven by the fluid 161. An organic orinorganic substance, such as silicon oil, air, water, or jelly, can beused as the fluid.

In the deformable mirror or the variable focal-length lens which usesthe electrostatic force or the piezoelectric effect, a high voltage issometimes required for drive. In this case, for example, as shown inFIG. 44, it is desirable that the boosting transformer or thepiezoelectric transformer is used to constitute the control system.

If the thin film 409 a for reflection is also provided in a portionwhich is not deformed, it can be used as a reference surface when theprofile of the deformable mirror is measured by an interferometer, whichis convenient.

FIG. 47 shows the structure of the variable focal-length lens used inthe imaging device according to the present invention. A variablefocal-length lens 511 includes a first lens 512 a having lens surfaces508 a and 508 b as a first surface and a second surface, respectively, asecond lens 512 b having lens surfaces 509 a and 509 b as a thirdsurface and a fourth surface, respectively, and a macromoleculardispersed liquid crystal layer 514 sandwiched between these lensesthrough transparent electrodes 513 a and 513 b. Incident light isconverged through the first and second lenses 512 a and 512 b. Thetransparent electrodes 513 a and 513 b are connected to analternating-current power supply 516 through a switch 515 so that analternating-current electric field is selectively applied to themacromolecular dispersed liquid crystal layer 514. The macromoleculardispersed liquid crystal layer 514 is composed of a great number ofminute macromolecular cells 518, each having any shape, such as a sphereor polyhedron, and including liquid crystal molecules 517, and itsvolume is equal to the sum of volumes occupied by macromolecules and theliquid crystal molecules 517 which constitute the macromolecular cells518.

Here, for the size of each of the macromolecular cells 518, for example,in the case of a sphere, when an average diameter is denoted by D andthe wavelength of light used is denoted by λ, the average diameter D ischosen to satisfy the following condition:2 nm≦D≦λ/5  (1)That is, the size of each of the liquid crystal molecules 517 is atleast about 2 nm and thus the lower limit of the average diameter D isset to about 2 nm or larger. The upper limit of the diameter D dependson a thickness t of the macromolecular dispersed liquid crystal layer514 in the direction of the optical axis of the variable focal-lengthlens 511. However, if the diameter is larger than the wavelength λ, adifference between the refractive indices of the macromolecules and theliquid crystal molecules 517 will cause light to be scattered at theinterfaces of the macromolecular cells 518 and will render the liquidcrystal layer 514 opaque. Hence, the upper limit of the diameter Dshould be λ/5 or less. A high degree of accuracy is not necessarilyrequired, depending on an optical product using the variablefocal-length lens. In this case, the diameter D below the value of thewavelength λ is satisfactory. Also, the transparency of themacromolecular dispersed liquid crystal layer 514 deteriorates withincreasing thickness t.

In the liquid crystal molecules 517, for example, uniaxial nematicliquid crystal molecules are used. The index ellipsoid of each of theliquid crystal molecules 517 is as shown in FIG. 48. That is,n_(ox)=n_(oy)=n_(o)  (2)where n_(o) is the refractive index of an ordinary ray and n_(ox) andn_(oy) are refractive indices in directions perpendicular to each otherin a plane including ordinary rays.

Here, in the case where the switch 515, as shown in FIG. 47 is turnedoff, that is, the electric field is not applied to the liquid crystallayer 514, the liquid crystal molecules 517 are oriented in variousdirections, and thus the refractive index of the liquid crystal layer514 relative to incident light becomes high to provide a lens withstrong refracting power. In contrast to this, when the switch 515, asshown in FIG. 49, is turned on and the alternating-current electricfield is applied to the liquid crystal layer 514, the liquid crystalmolecules 517 are oriented so that the major axis of the index ellipsoidof each liquid crystal molecule 517 is parallel with the optical axis ofthe variable focal-length lens 511, and hence the refractive indexbecomes lower to provide a lens with weaker refracting power.

The voltage applied to the macromolecular dispersed liquid crystal layer514, for example, as, shown in FIG. 50, can be changed stepwise orcontinuously by a variable resistor 519. By doing so, as the appliedvoltage becomes high, the liquid crystal molecules 517 are oriented sothat the major axis of the index ellipsoid of each liquid crystalmolecule 517 becomes progressively parallel with the optical axis of thevariable focal-length lens 511, and thus the refractive index can bechanged stepwise or continuously.

Here, in the case of FIG. 47, that is, in the case where the electricfield is not applied to the macromolecular dispersed liquid crystallayer 514, when the refractive index in the direction of the major axisof the index ellipsoid, as shown in FIG. 48, is denoted by n_(z), anaverage refractive index n_(LC)′ of the liquid crystal molecules 517 isroughly given by(n _(ox) +n _(oy) +n _(z))/3≡n _(LC)′  (3)Also, when the refractive index n_(z) is expressed as a refractive indexn_(e) of an extraordinary ray, an average refractive index n_(LC) whereEquation (2) is established is given by(2n ₀ +n _(e))/3≡n _(LC)  (4)In this case, when the refractive index of each of the macromoleculesconstituting the macromolecular cells 518 is represented by n_(p) andthe ratio of volume between the liquid crystal layer 514 and the liquidcrystal molecules 517 is represented by ff, a refractive index n_(A) ofthe liquid crystal layer 514 is given from the Maxwell-Garnet's law asn _(A) =ff·n _(LC)′+(1−ff)n _(p)  (5)

Thus, as shown in FIG. 50, when the radii of curvature of the innersurfaces of the lenses 512 a and 512 b, that is, the surfaces on theside of the liquid crystal layer 514, are represented by R₁ and R₂, afocal length f₁ of the variable focal-length lens 511 is given by1/f ₁=(n _(A)−1)(1/R ₁−1/R ₂)  (6)Also, when the center of curvature is located on the image side, it isassumed that the radius of curvature R₁ or R₂ is positive. Refractioncaused by the outer surface of each of the lenses 512 a and 512 b isomitted. That is, the focal length of the lens of only the liquidcrystal layer 514 is given by Equation (6).

When the average refractive index of ordinary rays is expressed as(n _(ox) +n _(oy))/2=n _(o)′  (7)a refractive index n_(B) of the liquid crystal layer 514 in the case ofFIG. 49, namely, in the case where the electric field is applied to theliquid crystal layer 514, is given byn _(B) =ff·n _(o)′+(1−ff)n _(p)  (8)and thus a focal length f₂ of the lens of only the liquid crystal layer514 in this case is given by1/f ₂=(n _(B)−1)(1/R ₁−1/R ₂)  (9)Also, the focal length where a lower voltage than in FIG. 49 is appliedto the liquid crystal layer 514 is a value between the focal length f₁given by Equation (6) and the focal length f₂ by Equation (9).

From Equations (6) and (9), a change rate of the focal length by theliquid crystal layer 514 is given by|(f ₂ −f ₁)/f ₂|=|(n _(B) −n _(A))/(n _(B)−1)|  (10)Thus, in order to increase the change rate, it is only necessary toincrease the value of |(n_(B)−n_(A))|. Here,n _(B) −n _(A) =ff(n _(o) ′−n _(LC)′)  (11)and hence if the value of |n_(o)′−n_(LC)′| is increased, the change ratecan be raised. Practically, since the refractive index n_(B) is about1.3–2, the value of |n_(o)′−n_(LC)′| is chosen so as to satisfy thefollowing condition:0.01≦|n _(o) ′−n _(LC)′|≦10  (12)In this way, when ff=0.5, the focal length obtained by the liquidcrystal layer 514 can be changed by at least 0.5%, and thus an effectivevariable focal-length lens can be realized. Also, the value of|n_(o)′−n_(LC)′| cannot exceed 10 because of restrictions on liquidcrystal substances.

Subsequently, a description will be given of grounds for the upper limitof Condition (1). The variation of a transmittance τ where the size ofeach cell of a macromolecular dispersed liquid crystal is changed isdescribed in “Transmission variation using scattering/transparentswitching films” on pages 197–214 of “Solar Energy Materials and SolarCells”, Wilson and Eck, Vol. 31, Eleesvier Science Publishers B. v.,1993. In FIG. 6 on page 206 of this publication, it is shown that whenthe radius of each cell of the macromolecular dispersed liquid crystalis denoted by r, t=300 μm, ff=0.5, n_(p)=1.45, n_(LC)=1.585, and λ=500nm, the theoretical value of the transmittance τ is about 90% if r=5 nm(D=λ/50 and D·t=λ·6 μm, where D and λ are expressed in nanometers), andis about 50% if r=25 nm (D=λ/10).

Here, it is assumed that t=150 μm and the transmittance τ varies as theexponential function of the thickness t. The transmittance τ in the caseof t=150 μm is nearly 71% when r=25 nm (D=λ/10 and D·t=λ·15 μm).Similarly, in the case of t=75 μm, the transmittance τ is nearly 80%when r=25 nm (D=λ/10 and D·t=λ·7.5 μm).

From these results, the transmittance τ becomes at least 70–80% and theliquid crystal can be actually used as a lens, if the liquid crystalsatisfies the following condition:D·t≦λ·15 μm  (13)Hence, for example, in the case of t=75 μm, if D≦λ/5, a satisfactorytransmittance can be obtained.

The transmittance of the macromolecular dispersed liquid crystal layer514 is raised as the value of the refractive index n_(p) approaches thevalue of the refractive index n_(LC)′. On the other hand, if the valuesof the refractive indices n_(o)′ and n_(p) are different from eachother, the transmittance of the liquid crystal layer 514 will bedegraded. In FIGS. 47 and 49, the transmittance of the liquid crystallayer 514 is improved on an average when the liquid crystal layer 514satisfies the following equation:n _(p)=(n _(o) ′+n _(LC)′)/2  (14)

The variable focal-length lens 511 is used as a lens, and thus in bothFIGS. 47 and 49, it is desirable that the transmittances are almost thesame and high. For this, although there are limits to the substances ofthe macromolecules and the liquid crystal molecules 517 constituting themacromolecular cells 518, it is only necessary, in practical use, tosatisfy the following condition:n _(o) ′≦n _(p) ≦n _(LC)′  (15)

When Equation (14) is satisfied, Condition (13) is moderated and it isonly necessary to satisfy the following condition:D·t≦λ·60 μm  (16)

It is for this reason that, according to the Fresnel's law ofreflection, the reflectance is proportional to the square of thedifference of the refractive index, and thus the reflection of light atthe interfaces between the macromolecules and the liquid crystalmolecules 517 constituting the macromolecular cells 518, that is, areduction in the transmittance of the liquid crystal layer 514, isroughly proportional to the square of the difference in refractive indexbetween the macromolecules and the liquid crystal molecules 517.

In the above description, reference has been made to the case wheren_(o)′≈1.45 and n_(LC)′≈1.585, but in a more general formulation, it isonly necessary to satisfy the following condition:D·t≦λ·15 μm·(1.585−1.45)²/(n _(u) −n _(p))²  (17)where (n_(u)−n_(p))² is a value when one of (n_(LC)′−n_(p))² and(n_(o)′−n_(p))² is larger than the other.

In order to largely change the focal length of the variable focal-lengthlens 511, it is favorable that the ratio ff is as high as possible, butin the case of ff=1, the volume of the macromolecule becomes zero andthe macromolecular cells 518 cease to be formable. Thus, it is necessaryto satisfy the following condition:0.1≦ff≦0.999  (18)

On the other hand, the transmittance τ improves as the ratio ff becomeslow, and hence Condition (17) may be moderated, preferably, as follows:4×10⁻⁶ [μm]² ≦D·t≦λ·45 μm·(1.585−1.45)²/(n _(u) −n _(p))²  (19)Also, the lower limit of the thickness t, as is obvious from FIG. 47,corresponds to the diameter D, which is at least 2 nm as describedabove, and therefore the lower limit of D·t becomes (2×10⁻³ μm)², namely4×10⁻⁶ [μm]².

An approximation where the optical property of substance is representedby the refractive index is established when the diameter D is 5–10 nm orlarger, as set forth in “Iwanami Science Library 8, Asteroids arecoming”, T. Mukai, Iwanami Shoten, p. 58, 1994. If the value of thediameter D exceeds 500 λ, the scattering of light will be changedgeometrically, and the scattering of light at the interfaces between themacromolecules and the liquid crystal molecules 517 constituting themacromolecular cells 518 is increased in accordance with the Fresnel'sequation of reflection. As such, in practical use, the diameter D mustbe chosen so as to satisfy the following condition:7 nm≦D≦500λ  (20)

FIG. 51 shows an imaging optical system for digital cameras using thevariable focal-length lens 511 of FIG. 50. In this imaging opticalsystem, an image of an object (not shown) is formed on the solid-stateimage sensor 523, such as a CCD, through a stop 521, the variablefocal-length lens 511, and a lens 522. Also, in FIG. 51, the liquidcrystal molecules are not shown.

According to such an imaging optical system, the alternating voltageapplied to the macromolecular dispersed liquid crystal layer 514 of thevariable focal-length lens 511 is controlled by the variable resistor519 to change the focal length of the variable focal-length lens 511.Whereby, without moving the variable focal-length lens 511 and the lens522 along the optical axis, it becomes possible to perform continuousfocusing with respect to the object distance, for example, from theinfinity to 600 mm.

FIG. 52 shows one example of a variable focal-length diffraction opticalelement applicable to the imaging device of the present invention. Thisvariable focal-length diffraction optical element 531 includes a firsttransparent substrate 532 having a first surface 532 a and a secondsurface 532 b which are parallel with each other and a secondtransparent substrate 533 having a third surface 533 a which isconstructed with an annular diffraction grating of saw-like crosssection having the depth of a groove corresponding to the wavelength oflight and a fourth surface 533 b which is flat. Incident light emergesthrough the first and second transparent substrates 532 and 533. Betweenthe first and second transparent substrates 532 and 533, as in FIG. 47,the macromolecular dispersed liquid crystal layer 514 is sandwichedthrough the transparent electrodes 513 a and 513 b so that thetransparent electrodes 513 a and 513 b are connected to thealternating-current power supply 516 through the switch 515 and thealternating-current electric field is applied to the macromoleculardispersed liquid crystal layer 514.

In such a structure, when the grating pitch of the third surface 533 ais represented by p and an integer is represented by m, a ray of lightincident on the variable focal-length diffraction optical element 531 isdeflected by an angle θ satisfying the following equation:p sin θ=mλ  (21)and emerges therefrom. When the depth of the groove is denoted by h, therefractive index of the transparent substrate 533 is denoted by n₃₃, andan integer is denoted by k, a diffraction efficiency becomes 100% at thewavelength λ and the production of flare can be prevented by satisfyingthe following equations:h(n _(A) −n ₃₃)=mλ  (22)h(n _(B) −n ₃₃)=kλ  (23)

Here, the difference in both sides between Equations (22) and (23) isgiven byh(n _(A) −n _(B))=(m−k)λ  (24)

Therefore, when it is assumed that λ=500 nm, n_(A)=1.55, and n_(B)=1.5,0.05 h=(m−k)·500 nm

and when m=1 and k=0,h=10000 nm=10 μm

In this case, the refractive index n₃₃ of the transparent substrate 533is obtained as 1.5 from Equation (22). When the grating pitch p on theperiphery of the variable focal-length diffraction optical element 531is assumed to be 10 μm, θ≈2.87° and a lens with an F-number of 10 can beobtained.

The variable focal-length diffraction optical element 531, whose opticalpath length is changed by the on-off operation of the voltage applied tothe liquid crystal layer 514, for example, can be used for focusadjustment in such a way that it is placed at a portion where the lightbeam of a lens system is not parallel, or can be used to change thefocal length of the entire lens system.

In the embodiment, it is only necessary that Equations (22)–(24) are setin practical use to satisfy the following conditions:0.7 mλ≦h(n _(A) −n ₃₃)≦1.4 mλ  (25)0.7 kλ≦h(n _(A) −n ₃₃)≦1.4 kλ  (26)0.7 (m−k)λ≦h(n _(A) −n _(B))≦1.4 (m−k)λ  (27)

A variable focal-length lens using a twisted nematic liquid crystal alsofalls into the category of the present invention. FIGS. 53 and 54 showvariable focal-length spectacles 550 in this case. The variablefocal-length lens 551 has lenses 552 and 553, orientation films 539 aand 539 b provided through the transparent electrodes 513 a and 513 b,respectively, inside these lenses, and a twisted nematic liquid crystallayer 554 sandwiched between the orientation films. The transparentelectrodes 513 a and 513 b are connected to the alternating-currentpower supply 516 through the variable resistor 519 so that thealternating-current electric field is applied to the twisted nematicliquid crystal layer 554.

In this structure, when the voltage applied to the twisted nematicliquid crystal layer 554 is increased, liquid crystal molecules 555, asillustrated in FIG. 54, exhibit a homeotropic orientation, in which therefractive index of the liquid crystal layer 554 is lower and the focallength is longer than in a twisted nematic condition of FIG. 53 in whichthe applied voltage is low.

A spiral pitch P of the liquid crystal molecules 555 in the twistednematic condition of FIG. 53 must be made nearly equal to, or muchsmaller than, the wavelength λ of light, and thus is set to satisfy thefollowing condition:2 nm≦P≦2 λ/3  (28)Also, the lower limit of this condition depends on the sizes of theliquid crystal molecules, while the upper limit is necessary for thebehavior of the liquid crystal layer 554 as an isotropic medium underthe condition of FIG. 53 when incident light is natural light. If theupper limit of the condition is overstepped, the variable focal-lengthlens 551 is changed to a lens in which the focal length varies with thedirection of deflection. Hence, a double image is formed and only ablurred image is obtained.

FIG. 55A shows a variable deflection-angle prism applicable to theimaging device of the present invention. A variable deflection-angleprism 561 includes a first transparent substrate 562 on the entranceside, having a first surface 562 a and a second surface 562 b; and asecond transparent substrate 563 of a plane-parallel plate on the exitside, having a third surface 563 a and a fourth surface 563 b. The innersurface (the second surface) 562 b of the transparent substrate 562 onthe entrance side is configured into a Fresnel form, and themacromolecular dispersed liquid crystal layer 514, as in FIG. 47, issandwiched, through the transparent electrodes 513 a and 513 b, betweenthe transparent substrate 562 and the transparent substrate 563 on theexit side. The transparent electrodes 513 a and 513 b are connected tothe alternating-current power supply 516 through the variable resistor519. Whereby, the alternating-current electric field is applied to theliquid crystal layer 514 so that the deflection angle of lighttransmitted through the variable deflection-angle prism 561 iscontrolled. Also, in FIG. 55A, the inner surface 562 b of thetransparent substrate 562 is configured into the Fresnel form, but asshown in FIG. 55B, the inner surfaces of the transparent substrates 562and 563 may be configured like an ordinary prism whose surfaces arerelatively inclined, or may be configured like the diffraction gratingshown in FIG. 52. In the case of the latter, when Equations (21)–(24)and Conditions (25)–(27) are satisfied, the same description as in thevariable focal-length diffraction optical element 531 and the variablefocal-length spectacles 550 is applied.

The variable deflection-angle prism 561 constructed mentioned above canbe effectively used for shake prevention for TV cameras, digitalcameras, film cameras, binoculars, etc. In this case, it is desirablethat the direction of refraction (deflection) of the variabledeflection-angle prism 561 is vertical, but in order to further improveits performance, it is desirable that two variable deflection-angleprisms 561 are arranged so that the directions of deflection are variedand as shown in FIG. 56, the refraction angles are changed in verticaland lateral directions. Also, in FIGS. 55A, 55B, and 56, the liquidcrystal molecules are omitted.

FIG. 57 shows a variable focal-length mirror applying the variablefocal-length lens used in the imaging device according to the presentinvention. A variable focal-length mirror 565 includes a firsttransparent substrate 566 having a first surface 566 a and a secondsurface 566 b, and a second transparent substrate 567 having a thirdsurface 567 a and a fourth surface 567 b. The first transparentsubstrate 566 is configured into a flat plate or lens shape to providethe transparent electrode 513 a on the inner surface (the secondsurface) 566 b. The second transparent substrate 567 is such that theinner surface (the third surface) 567 a is configured as a concavesurface, on which a reflecting film 568 is deposited, and thetransparent electrode 513 b is provided on the reflecting film 568.Between the transparent electrodes 513 a and 513 b, as in FIG. 47, themacromolecular dispersed liquid crystal layer 514 is sandwiched so thatthe transparent electrodes 513 a and 513 b are connected to thealternating-current power supply 516 through the switch 515 and thevariable resistor 519, and the alternating-current electric field isapplied to the macromolecular dispersed liquid crystal layer 514. Also,in FIG. 57, the liquid crystal molecules are omitted.

According to the above structure, since a ray of light incident on thetransparent substrate 566 is passed again through the liquid crystallayer 514 by the reflecting film 568, the function of the liquid crystallayer 514 can be exercised twice, and the focal position of reflectedlight can be shifted by changing the voltage applied to the liquidcrystal layer 514. In this case, the ray of light incident on thevariable focal-length mirror 565 is transmitted twice through the liquidcrystal layer 514, and therefore when a thickness twice that of theliquid crystal layer 514 is represented by t, Conditions mentioned abovecan be used. Moreover, the inner surface of the transparent substrate566 or 567, as shown in FIG. 52, can also be configured into thediffraction grating shape to reduce the thickness of the liquid crystallayer 514. By doing so, the amount of scattered light can be decreased.

In the above description, in order to prevent the deterioration of theliquid crystal, the alternating-current power supply 516 is used as avoltage source to apply the alternating-current electric field to theliquid crystal. However, a direct-current power supply is used andthereby a direct-current electric field can also be applied to theliquid crystal. Techniques of shifting the orientation of the liquidcrystal molecules, in addition to changing the voltage, can be achievedby changing the frequency of the electric field applied to the liquidcrystal, the strength and frequency of the magnetic field applied to theliquid crystal, or the temperature of the liquid crystal. In the aboveembodiments, since the macromolecular dispersed liquid crystal is closeto a solid, rather than a liquid, one of the lenses 512 a and 512 b, thetransparent substrate 532, the lens 522, one of the lenses 552 and 553,the transparent substrate 563 of FIG. 55A, or one of the transparentsubstrates 562 and 563 of FIG. 55B, may be eliminated. Also, in thepresent invention, it is assumed that the variable focal-length mirrorwhose profile is not changed, such as that in FIG. 57, falls under theclass of the deformable mirror.

FIG. 58 shows an imaging unit 141 using a variable focal-length lens 140in another embodiment of the variable focal-length lens used in theimaging device of the present invention. The imaging unit 141 can beused as the imaging system of the present invention. In this embodiment,the lens 102 and the variable focal-length lens 140 constitute animaging lens system, and the imaging lens system and the solid-stateimage sensor 408 constitute the imaging unit 141. The variablefocal-length lens 140 is constructed with a light-transmitting fluid orjelly-like substance 144 sandwiched between a transparent member 142 anda soft transparent substance 143 such as piezoelectric synthetic resin.

As the fluid or jelly-like substance 144, silicon oil, elastic rubber,jelly, or water can be used. Transparent electrodes 145 are provided onboth surfaces of the transparent substance 143, and when the voltage isapplied through a circuit 103′, the transparent substance 143 isdeformed by the piezoelectric effect of the transparent substance 143 sothat the focal length of the variable focal-length lens 140 is changed.

Thus, according to the embodiment, even when the object distance ischanged, focusing can be performed without moving the optical systemwith a motor, and as such the embodiment excels in compact andlightweight design and low power consumption.

In FIG. 58, reference numeral 146 denotes a cylinder for storing afluid. For the transparent substance 143, high-polymer piezoelectricssuch as polyurethane, silicon rubber, acrylic elastomer, PZT, PLZT, andPVDF; vinylidene cyanide copolymer; or copolymer of vinylidene fluorideand trifluoroethylene is used.

The use of an organic substance, synthetic resin, or elastomer, having apiezoelectric property, brings about a considerable deformation of thesurface of the deformable mirror, which is favorable. It is goodpractice to use a transparent piezoelectric substance for the variablefocal-length lens.

In FIG. 58, instead of using the cylinder 146, the variable focal-lengthlens 140, as shown in FIG. 59, may be designed to use supporting members147. The supporting members 147 are designed to fix the periphery of apart of the transparent substance 143 sandwiched between the transparentelectrodes 145. According to the embodiment, even when the voltage isapplied to the transparent substance 143 and thereby the transparentsubstance 143 is deformed, as shown in FIG. 60, the volume of the entirevariable focal-length lens 140 remains unchanged. As such, the cylinder146 becomes unnecessary. Also, in FIGS. 59 and 60, reference numeral 148designates a deformable member, which is made with an elastic body,accordion-shaped synthetic resin, or metal.

In each of the examples shown in FIGS. 58 and 59, when a reverse voltageis applied, the transparent substance 143 is deformed in a reversedirection, and thus it is also possible to construct a concave lens.

Where an electrostrictive substance, for example, acrylic elastomer orsilicon rubber, is used for the transparent substance 143, it isdesirable that the transparent substance 143 is constructed so that thetransparent substrate and the electrostrictive substance are cemented toeach other.

FIG. 61 shows a variable focal-length lens 167 in which the fluid 161 istaken in and out by a micropump 160 to deform the lens surface, inanother embodiment of the variable focal-length lens used in the imagingdevice of the present invention.

The micropump 160 is a small-sized pump, for example, made by amicromachining technique and is constructed so that it is operated withan electric power. The fluid 161 is sandwiched between a transparentsubstrate 163 and an elastic body 164. In FIG. 61, reference numeral 165represents a transparent substrate for protecting the elastic body 164and this substrate is not necessarily required.

As examples of pumps made by the micromachining technique, there arethose which use thermal deformations, piezoelectric substances, andelectrostatic forces.

It is also possible to use the micropump 180 shown in FIG. 46 as twomicropumps, for example, as in the micropump 160 used in the variablefocal-length lens 167 of FIG. 61.

In the variable focal-length lens which uses the electrostatic force orthe piezoelectric effect, a high voltage is sometimes required fordrive. In this case, it is desirable that the boosting transformer orthe piezoelectric transformer is used to constitute the control system.When a laminated piezoelectric transformer is particularly used, acompact design is achieved.

FIG. 62 shows a variable focal-length lens 201 using a piezoelectricsubstance 200 in another embodiment of the variable optical-propertyoptical element applicable to the imaging device of the presentinvention.

The same substance as the transparent substance 143 is used for thepiezoelectric substance 200, which is provided on a soft transparentsubstrate 202. It is desirable that synthetic resin or an organicsubstance is used for the substrate 202.

In this embodiment, the voltage is applied to the piezoelectricsubstance 200 through the two transparent electrodes 59, and thereby thepiezoelectric substance 200 is deformed so that the function of a convexlens is exercised in FIG. 62.

The substrate 202 is previously configured into a convex form, and atleast one of the two transparent electrodes 59 is caused to differ insize from the substrate 202, for example, one of the electrodes 59 ismade smaller than the substrate 202. In doing so, when the appliedvoltage is removed, the opposite, preset portions of the two transparentelectrodes 59, as shown in FIG. 63, are deformed into concave shapes soas to have the function of a concave lens, acting as the variablefocal-length lens.

In this case, since the substrate 202 is deformed so that the volume ofthe fluid 161 is not changed, there is the merit that the liquid tank168 becomes unnecessary.

This embodiment has a great merit that a part of the substrate holdingthe fluid 161 is deformed by the piezoelectric substance and the liquidtank 168 is dispensed with.

The transparent substrates 163 and 165 may be constructed with lenses orplane surfaces, and the same may be said of the embodiment of FIG. 61.

FIG. 64 shows a variable focal-length lens using two thin plates 200Aand 200B constructed of piezoelectric substances in still anotherembodiment of the variable optical-property optical element applicableto the imaging device of the present invention.

The variable focal-length lens of this embodiment has the merit that thethin plate 200A is reversed in direction of the substance with respectto the thin plate 200B, and thereby the amount of deformation isincreased so that a wide variable focal-length range can be obtained.Also, in FIG. 64, reference numeral 204 denotes a lens-shapedtransparent substrate. Even in the embodiment, the transparent electrode59 on the right side of the figure is configured to be smaller than thesubstrate 202.

In the embodiments of FIGS. 62–64, the thicknesses of the substrate 202,the piezoelectric substance 200, and the thin plates 200A and 200B maybe rendered uneven so that a state of deformation caused by theapplication of the voltage is controlled. By doing so, lens aberrationcan be corrected, which is convenient.

FIG. 65 shows another embodiment of the variable focal-length lens usedin the imaging device of the present invention. A variable focal-lengthlens 207 of this embodiment uses an electrostrictive substance 206 suchas silicon rubber or acrylic elastomer.

According to the embodiment, when the voltage is low, theelectrostrictive substance 206, as depicted in FIG. 65, acts as a convexlens, while when the voltage is increased, the electrostrictivesubstance 206, as depicted in FIG. 66, expands in a vertical directionand contracts in a lateral direction, and thus the focal length isincreased. In this way, the electrostrictive substance 206 operates asthe variable focal-length lens. According to the variable focal-lengthlens of the embodiment, there is the merit that since a large powersupply is not required, power consumption is minimized.

FIG. 67 shows a variable focal-length lens using a photomechanicaleffect in a further embodiment of the variable optical-property opticalelement applicable to the imaging device of the present invention. Avariable focal-length lens 214 of this embodiment is designed so thatazobenzene 210 is sandwiched between transparent elastic bodies 208 and209 and is irradiated with light through a transparent spacer 211. InFIG. 67, reference numerals 212 and 213 represent light sources, such asLEDs or semiconductor lasers, of central wavelengths λ₁ and λ₂,respectively.

In the embodiment, when trans-type azobenzene shown in FIG. 68A isirradiated with light of the central wavelength λ₁, the azobenzene 210changes to cis-type azobenzene shown in FIG. 68B to reduce its volume.Consequently, the thickness of the variable focal-length lens 214 isdecreased, and the function of the convex lens is impaired.

On the other hand, when the cis-type azobenzene is irradiated with lightof the central wavelength λ₂, the azobenzene 210 changes to thetrans-type azobenzene to increase the volume. Consequently, thethickness of the variable focal-length lens 214 is increased, and thefunction of the convex lens is improved.

In this way, the optical element of the embodiment acts as the variablefocal-length lens. In the variable focal-length lens 214, since thelight is totally reflected at the interface between each of thetransparent elastic bodies 208 and 209 and air, the light does not leakthrough the exterior and high efficiency is obtained. Also, thewavelength of light utilized for the lens may be that of infrared light,not to speak of visible light. For the azobenzene 210, a mixture ofazobenzene and another liquid may be used.

FIG. 69 shows another embodiment of the deformable mirror used as thevariable mirror in the imaging device according to the presentinvention. In this embodiment, the deformable mirror is used in thedigital camera. The deformable mirror 409 of the embodiment is such thatthe divided electrodes 409 b are spaced away from the electrostrictivesubstance 453 including an organic substance such as acrylic elastomer,on which an electrode 452 and the deformable substrate 451 are placed inturn, and a reflecting film 450 including metal, such as aluminum, forreflecting incident light is provided on the substrate 451.

The deformable mirror, when constructed as mentioned above, has themerit that the surface of the reflecting film 450 becomes smooth and itis hard to optically produce aberration, in contrast to the case wherethe divided electrodes 409 b and the electrostrictive substance 453 areintegrally constructed. Also, the deformable substrate 451 and theelectrode 452 may be arranged in reverse order.

In FIG. 69, reference numeral 449 stands for a button for changing themagnification of the optical system or zooming. The deformable mirror409 is controlled through the arithmetical unit 414 so that a userpushes the button 449 and thereby the reflecting film 450 can bedeformed to change the magnification or zoom. Also, instead of theelectrostrictive substance including an organic substance such asacrylic elastomer, the piezoelectric substance such as barium titanatemay be used.

In the above description, reference has been made to the control anddrive of the variable optical-property optical element using the LUT.Most of the embodiments refer to the imaging devices, but the presentinvention is applied to the whole of the optical apparatus including adisplay device or an observation device which uses the variableoptical-property optical element, not to speak of the imaging device.Also, although reference has been chiefly made to the control of thevariable mirror, the present invention is not limited to this and isalso applicable to the control of the variable optical-property opticalelement such as the variable focal-length lens.

In a projection device or display device such as a liquid crystalprojector, “the distance to the object” in the present invention isthought of as a distance to a projected image. That is, when an imageand an object are conjugate, the present invention is applicable to thedisplay device or the observation device.

Finally, the terms used in the present invention will be described.

An optical apparatus used in the present invention refers to anapparatus including an optical system or optical elements. The opticalapparatus need not necessarily function by itself. That is, it may bethought of as a part of an apparatus. The optical apparatus includes animaging device, an observation device, a display device, an illuminationdevice, and a signal processing device.

The imaging device refers to, for example, a film camera, a digitalcamera, a digital camera for cellular phones, a robot's eye, alens-exchangeable digital single-lens reflex camera, a TV camera, amoving-picture recorder, an electronic moving-picture recorder, acamcorder, a VTR camera, or an electronic endoscope. Any of the digitalcamera, a card digital camera, the digital camera for cellular phones,the TV camera, the VTR camera, and a moving-picture recording camera isan example of an electronic imaging device.

The observation device refers to, for example, a microscope, atelescope, spectacles, binoculars, a magnifier, a fiber scope, a finder,or a viewfinder.

The display device includes, for example, a liquid crystal display, aviewfinder, a game machine (Play Station by Sony), a video projector, aliquid crystal projector, a head mounted display (HMD), a personaldigital assistant (PDA), or a cellular phone.

The illumination device includes, for example, a stroboscopic lamp forcameras, a headlight for cars, a light source for endoscopes, or a lightsource for microscopes.

The signal processing device refers to, for example, a cellular phone, apersonal computer, a game machine, a read/write device for opticaldisks, or an arithmetic unit for optical computers.

The image sensor refers to, for example, a CCD, a pickup tube, asolid-state image sensor, or a photographing film. The plane-parallelplate is included in one of prisms. A change of an observer includes achange in diopter. A change of an object includes a change in objectdistance, the displacement of the object, the movement of the object,vibration, or the shake of the object.

An extended surface is defined as follows:

Each of the surfaces of lenses, prisms, and mirrors need not necessarilybe planar, and may have any shape such as a spherical or rotationallysymmetrical aspherical surface; a spherical, planar, or rotationallysymmetrical aspherical surface which is decentered with respect to theoptical axis; an aspherical surface with symmetrical surfaces; anaspherical surface with only one symmetrical surface; an asphericalsurface with no symmetrical surface; a free-formed surface; a surfacewith a nondifferentiable point or line; etc. Moreover, any surface whichhas some effect on light, such as a reflecting or refracting surface, issatisfactory. In the present invention, it is assumed that such asurface is generally referred as to the extended surface.

The variable optical-property optical element includes a variablefocal-length lens, a deformable mirror, a deflection prism whose surfaceprofile is changed, a variable angle prism, a variable diffractionoptical element in which the function of light deflection is changed,namely a variable HOE, or a variable DOE.

Also, in the present invention, information used for the control of thevariable optical-property optical element relative to the current or thevoltage is referred to as drive information.

The variable focal-length lens also includes a variable lens such thatthe focal length is not changed, but the amount of aberration ischanged. The same holds for the case of the deformable mirror. In aword, an optical element in which the function of light deflection, suchas reflection, refraction, or diffraction, can be changed is called thevariable optical-property optical element.

An information transmitter refers to a device which is capable ofinputting and transmitting any information from a cellular phone; astationary phone; a remote control for game machines, TVs,radio-cassette tape recorders, or stereo sound systems; a personalcomputer; or a keyboard, mouse, or touch panel for personal computers.It also includes a TV monitor with the imaging device, or a monitor ordisplay for personal computers. The information transmitter is includedin the signal processing device.

1. An optical apparatus having a variable optical-property opticalelement, wherein a deformed profile of an optical surface of saidvariable optical-property optical element where said variableoptical-property optical element is driven is measured by a measurementdevice or assumed, a measured value or an assumed value of said deformedprofile is compared with an optical design value of an optimum profileof said variable optical property optical element corresponding to oneof a zoom state, a distance to an object, and both to adjust a value ofa voltage applied or a current supplied to said variable opticalproperty optical element so that said measured value or said assumedvalue of said deformable profile corresponds with said optical designvalue of said optimum profile within tolerances, and said value of saidvoltage applied or said current supplied to said variableoptical-property optical element where said measured value or saidassumed value of said deformable profile coincides with said opticaldesign value of said optimum profile within tolerances is stored inoutput information as an optimum voltage value to be applied or anoptimum current value to be supplied to said variable optical-propertyoptical element to thereby make a look-up table.
 2. An optical apparatushaving a variable optical-property optical element, wherein an opticalproperty of said variable optical-property optical element where saidvariable optical-property optical element is driven is measured by ameasuring device or assumed, a measured value or an assumed value ofsaid optical property is compared with an optical design value of saidoptical property of said variable optical-property optical elementcorresponding to one of a zoom state, a distance to an object, and bothto adjust driving information for driving said variable optical-propertyoptical element so that said measured value or said assumed value ofsaid optical property coincides with said optical design value of saidoptical property within tolerances, and a value of said drivinginformation provided to said variable optical-property optical elementwhere said measured value or said assumed value of said optical propertycoincides with said optical design value of said optical property isstored in output information as driving information to be provided tosaid variable optical-property optical element to thereby make a look-uptable.
 3. An optical apparatus having a variable optical-propertyoptical element, wherein a voltage is applied or a current is suppliedto said variable optical-property optical element, a sharpness of animage formed by said optical apparatus having said variableoptical-property optical element corresponding to one of a zoom state, adistance to an object, and both is evaluated to adjust a value of saidvoltage applied or said current supplied to said variableoptical-property optical element, and said value of said voltage appliedor said current supplied to said variable optical-property opticalelement where said sharpness is optimized within tolerances is stored inoutput information as an optimum voltage value to be applied or anoptimum current value to be supplied to said variable optical-propertyoptical element to thereby make a look-up table.
 4. An optical apparatushaving a variable optical-property optical element, wherein saidvariable optical-property optical element is driven, a sharpness of animage formed by said optical apparatus having said variableoptical-property optical element corresponding to one of a zoom state, adistance to an object, and both is evaluated to adjust a value ofdriving information provided to said variable optical-property opticalelement, and said value of said driving information provided to saidvariable optical-property optical element where said sharpness isoptimized within tolerances is stored in output information as optimumdriving information to be provided to said variable optical-propertyoptical element to thereby make a look-up table.
 5. An optical apparatushaving a variable optical-property optical element, wherein anapproximate curve table of an optimum voltage to be applied or anoptimum current to be supplied to said variable optical-property opticalelement is provided corresponding to one of a zoom state, a distance toan object, and both and a value of said optimum voltage to be applied orsaid optimum current to be supplied to said variable optical-propertyoptical element is calculated by an approximate equation obtained fromsaid approximate curve table in accordance with one of said zoom state,said distance to the object, and both in image formation so that avoltage or current of an optimum value obtained thereform is applied orsupplied to said variable optical-property optical element.
 6. Anoptical apparatus having a variable optical-property optical element,wherein an approximate curve table of an optimum voltage to be appliedor an optimum current to be supplied to said variable optical-propertyoptical element is provided corresponding to one of a zoom state, adistance to an object, and both and a value of said optimum voltage tobe applied or said optimum current to be supplied to said variableoptical-property optical element is calculated by an approximateequation obtained from said approximate curve table in accordance withone of said zoom state, said distance to the object, and both in imageformation so that a voltage or current of an optimum value obtainedthereform is applied or supplied to said variable optical-propertyoptical element to thereby drive said variable optical-property opticalelement.
 7. An imaging device having a zoom optical system, comprising:an image sensor, a moving lens unit, and a plurality of variablemirrors, wherein said moving lens unit contributes to a magnificationchange of said optical system and said variable mirrors contributes toone of focusing, compensation for a focus shift in said magnificationchange, compensation for fluctuation of aberration, and saidmagnification change, and wherein the plurality of variable mirrors areseparately arranged from one another.
 8. An imaging device according toclaim 7, wherein a device configured to detect a position of said lensunit is provided.
 9. An imaging device according to claim 8, wherein thedevice that detects a position of said lens unit is an encoder or astepping motor.
 10. An imaging device having a zoom optical system,comprising: an image sensor, a moving lens unit, and a plurality ofvariable mirrors, wherein said moving lens unit performs a magnificationchange of said optical system and said variable mirrors performs atleast one of focusing, compensation for a focus shift in saidmagnification change, compensation for fluctuation of aberration, andsaid magnification change, and wherein the plurality of variable mirrorsare separately arranged from one another.
 11. An imaging device having azoom optical system, comprising: a lens unit with a rotationallysymmetrical surface, and a plurality of variable mirrors, wherein saidvariable mirrors contributes to one of focusing, compensation for afocus shift in a magnification change of said optical system,compensation for fluctuation of aberration, and said magnificationchange, and wherein the plurality of variable mirrors are separatelyarranged from one another.
 12. An optical apparatus, comprising: avariable optical-property optical element, an active auto-focus systemconfigured to measure a distance to an object or an image, wherein saidvariable optical-property optical element is driven based on distanceinformation from said auto-focus system to perform focusing.
 13. Anoptical apparatus according to claim 12, wherein an optical system thatperforms one-lens-unit zooming is provided.
 14. An optical apparatus,comprising: a variable optical-property optical element, a plurality ofdriving circuits for driving said variable optical-property opticalelement, and a control information-providing system that providescontrol information used for operating the optical apparatus in anoptimum image forming state, the control information being prepared tocontrol the variable optical-property optical element so that images ofobjects arranged at a plurality of places in an imaging area areproperly formed.
 15. An optical apparatus, comprising: a variableoptical-property optical element, a plurality of driving circuits fordriving said variable optical-property optical element, and a controlinformation-providing system that provides control information used foroperating the optical apparatus in an optimum image forming state, thecontrol information being prepared to control the variableoptical-property optical element so that images of objects arranged at aplurality of places in an imaging area are properly formed to compensatea manufacturing error of said optical apparatus.